In order to promote Jiangsu province to take the lead in achieving carbon peak in China, this paper studies the coupling de-gree of socioeconomic and ecological environment system in Nanjing city. The coupling evaluation index system of socioeconomic system and ecological environment sys-tem was established, the weight of each evaluation index and the comprehensive evaluation index were calculated by adopting entropy weighting method, and the coupling degree model of the two systems was constructed. And the coupling degree and coupling coordination type of the socioeconomic system and ecological environment system in Nanjing were ana-lyzed empirically. The results show that: ( 1) in the past 10 years, the level of social economy development in Nanjing has been rising steadily year by year, and the development level of ecological environment has been on the rise although there are fluctuations, and the rising trend of socioeconomic system is greater than that of ecological environment system; ( 2) The coupling between social economy and ecological environment system in Nanjing changed greatly from 2010 to 2015, and the two systems are in the stage of constant adjustment and adaptation. Since 2015, the coupling between the two systems has become increasingly perfect.