 This study examined the performance of China's marine green economy over the period 2006 to 2018 using a two-stage network data envelopment analysis, DEA, model. It found that the overall efficiency of the marine green economy has been declining since 2006, with the exception of 2014. The study also identified several key factors affecting the performance of the marine green economy, including foreign direct investment, FDI, opening up, industrial development level, and marine economic development level. FDI had a significant positive effect on total efficiency while opening up had a negative effect. Industrial development level and marine economic development level both had a negative effect on total efficiency. The study concluded that these factors should be taken into consideration when developing policies for the marine green economy.