数字经济具有外部性，省会城市数字经济发展对其它邻近城市的影响究竟是比翼齐飞的溢出效应，还是损人利己的虹吸效应？回答该问题对当前“强省会”战略实施和区域协调发展至关重要。从收入产出、劳动和资本投入角度构建理论模型，采用2011—2019年278个地级市面板数据，运用面板固定模型实证检验省会城市数字经济发展对地方城市的影响。结果显示：①省会城市数字经济发展促进地方城市数字经济发展，且溢出效应显著，一系列内生性和稳健性检验均证实该结论成立；②省会城市数字经济溢出效应的南北差距不明显，溢出效应主要发生在东中部地区，中等规模城市的溢出效应明显高于小规模和大规模城市；③省会城市数字经济溢出效应并不能通过分工机制予以解释，而是通过学习机制和共享机制实现。为此，需要深入实施“强省会”战略，发挥省会城市的引领示范辐射作用；坚持因地制宜发展原则，构建数字经济错位发展格局；明确省会城市和地方城市数字经济发展定位，充分释放数字经济潜能，打造分工协作的产业链条。

As the main spatial carrier of economic and social development, many cities in China have successively introduced the strategy of"strengthening provincial capitals" in recent years. Then, with the implementation of this strategy, it may bring the spillover of provincial capital city resources,promote the development of local digital economy,and also lead provincial capital cities to absorb a large amount of digital resources, forming the digital economy gap between provincial capital cities and local cities. Do provincial capitals gather digital resources because of their own advantages of economic size, population size, and capital policy, thus producing a "siphon effect" on surrounding cities; or do they make full use of their own resource sharing and joint construction mechanism to drive the economic development of surrounding local cities, and then realize rapid growth together? This problem is crucial for the implementation of the current strategy of "strengthening provincial capitals" and the coordinated development of regions.#br#There is a lack of a standard evaluation index system in the existing research, and no academic consensus on the development measurement of the digital economy. Therefore, this paper selects indicators from the perspective of output and input, constructs a theoretical model that can reveal the "spillover effect" and "siphon effect" of the development of digital economy in provincial capital cities, and effectively avoids the controversy about digital economy evaluation. In terms of the externality characteristics of the digital economy, scholars believe that the digital economy can have an impact on the surrounding areas through technology diffusion and knowledge spillover. The digital economy has promoted the flow of related labor and capital, and accelerated the formation of industrial specialization among regions. The digital economy promotes the communication between regions through mutual assistance and sharing mechanism. Therefore, this paper further tries to explain the influence of digital economy on local cities by using division of labor mechanism, learning mechanism and sharing mechanism.#br#The panel fixed model is used to study the spillover effect of digital economy development in provincial capital cities on other cities in the province based on city panel data from 2011 to 2019 . The empirical results show that (1) the development of digital economy in provincial capital cities has improved the development of digital economy in local cities, and the spillover effect is obvious, and a series of endogenous and robustness tests have confirmed this view; (2) the north-south gap between the spillover effect of digital economy in provincial capital cities is not obvious, which mainly occurs in the eastern and central regions; the spillover effect in medium-sized cities is significantly higher than that of small-size and large-size cities; (3) the spillover effect of digital economy in provincial capitals cannot be well explained by the division of labor mechanism. This spillover effect is mainly realized through the learning mechanism and partly through the sharing mechanism.#br#With a focus on the externalities of digital economy, this study firstly discusses the influence of provincial capitals on local cities from the strategy of "strengthening provincial capitals", thus expanding the new perspective of related research on digital economy. Then the labor input, capital input and income-output indicators are included to construct a theoretical model of "spillover effect" and "siphon effect" of digital economy in provincial capital cities, and it reveals the function mechanism of provincial capital cities on the development of digital economy in local cities. Thirdly since cities are the best carries for the implementation of digital economy policies, this study uses the urban panel data to explore the influence of provincial capitals on local cities, which is realistic and deepens the existing literature.#br#The results of this paper have certain guiding significance for the development of digital economy in provincial capitals. The government should adhere to the implementation of the "strengthening provincial capitals" strategy, give full play to the leading role of provincial capitals demonstration radiation. It is also essential to hold onto the principle of adapting measures to local conditions, and give full consideration to the differences in the development of digital economy in different regions. Besides the government ought to clarify the development orientation of digital economy in provincial capitals and local governments, strengthen the learning and sharing mechanism of digital economy, and build a complete industrial chain.#br#