As a national strategic industry undertaking the dual mission of national defense construction and economic development, the national defense industry is the field with themost concentratednational defense science and technology innovation, and it is also an important symbol reflecting the level of national defense science and technology. In recent years, in the background of the complex and changeable international situation, the improvement of national defense science and technology innovation, especially the improvement of independent innovation capabilities, has attracted more and more attention from scholars. Most focus on the influencing factors of national defense science and technology innovation, leaving the examination of China's national defense science and technology innovation capabilities and levels rarely touched. Only a small number of scholars have also made preliminary calculations of the innovation of China's national defense science and technology industry, and these documents have measured the total factor productivity, technological progress and technological efficiency of some listed military enterprises, as well as the comprehensive technical efficiency, technical efficiency and scale efficiency of some military enterprises. But most of the research uses the data of listed military enterprises, and its innovation efficiency level does not fully represent the overall innovation level of the entire national defense science and technology industry, nor can it better explain the specific sources of changes in national defense scientific and technological innovation capabilities. #br#Therefore, this paper focuses on analyzing the current scientific and technological innovation capabilities and levels of China's national defense industry, that is, calculating the innovation of China's national defense science and technology industry, so as to more accurately understand the technological progress of China's national defense industry and better grasp the innovation level of national defense science and technology industry. Moreover it makes further improvements on the basis of existing research. First, the data of large-scale military enterprise group co., LTD. is used so that the calculation results can better represent the main body of China's national defense science and technology industry. Second, the LP method is used for calculation, and the intermediate input replaces the investment in the OP method as a proxy variable, so that the calculation results are more accurate. Third the study not only analyzes the overall characteristics of the total factor productivity of the national defense industry , the change characteristics of subdivided industries and enterprises, it also make comparison between manufacturing and high-tech industries, thus the analysis is more comprehensive.#br#This paper uses the financial report data of China’s 11 large-scale military enterprise group co., LTD. from 2004 to 2020 to calculate the total factor productivity of the defense industry from the micro perspective of the enterprises and analyzes the trend. The results of the study show that during the sample period, the total factor productivity of China's national defense industry is generally fluctuating, and the growth rate is higher than the overall manufacturing level but lower than the growth rate of high-tech industries, indicating that the technological progress of the national defense industry is more obvious, but the rate of progress is not fast enough; there are large differences in the total factor productivity of various subdivisions of the military industry, and the average total factor productivity of the electronics industry and the shipbuilding industry is higher than that of other military industries; the convergence analysis shows that enterprises with low total factor productivity in the national defense industry have a higher rate of enterprises catch-up effect.#br#This paper synthesizes the research results in related fields such as the total factor productivity measurement method of micro enterprises, the technical efficiency measurement and analysis of military enterprises, and the convergence test, and studies the total factor productivity measurement and analysis of military enterprises,providing a reference for further research. The research results have important guiding significance for how to improve the ability of national defense science and technology innovation. The military industry must change its growth model, change to an intensive direction and improve the quality of development. At the same time, the government should increase investment in research and development, provide preferential policies, funds, and technical support to industries with relatively slow technological development, promote the coordinated development of the military industry, and implement the military-civilian integration development strategy and promote the conversion of advanced civilian technology to military use.#br#