Abstract: Marine resources and environmental carrying capacity is an index to assess the ability of marine resources and environment systems to carry human activities. In order to uncover the changing trends and key influencing factors of marine resources and environmental carrying capacity in Weifang City, an evaluation system of marine resources and environmental carrying capacity is constructed by selecting 25 indicators from three subsystems of marine economic development, marine resources carrying capacity and marine environmental carrying capacity. Then, the marine resources and environmental carrying capacity and the capacity levels of the three subsystems in Weifang during 2010—2019 are evaluated by using entropy weight TOPSIS model. The correlation degree between the evaluation indicators and the marine resources and environmental carrying capacity is analyzed by using gray correlation method and the key influencing factors are identified. The results show that as a whole the carrying capacity level of marine resources and environment in Weifang showed a fluctuating upward trend from 2010 to 2019, of which a slightly decreasing trend occurred from 2010 to 2012, an obvious upward trend from 2013 to 2016, a decline trend in 2017 and afterward maintained a steady upward trend. The development level of marine economy showed a steady upward trend, whereas the carrying capacity of marine resources had a fluctuating downward trend. Obviously, the carrying pressure of marine resources is great. The level of the marine environmental carrying capacity is overall in a fluctuating rising state, which is basically consistent with the changing trend of marine resources and environmental carrying capacity in Weifang. The key factors affecting the marine resources and environmental carrying capacity in Weifang are the compliance rate of industrial wastewater discharge and the amount of industrial wastewater discharged per unit area. It is, therefore, suggested that the scientific development of marine economy in Weifang should be on the basis of the local resources and environmental endowment and formulate a medium- and long-term marine strong city development plan. Meanwhile, the sustainable utilization of marine resources and the protection of marine ecological environment should also be focused, so that the high-quality development of marine economy in Weifang can be promoted.