Abstract: Marine ranching is one of the key measures for the conservation of marine fishery resources and environmental restoration in Guangdong Province. To systematically evaluate the ecological benefits of marine ranching construction in Guangdong Province, we applied Entropy Weight Method (EWM) and Fuzzy Matter Element Method (FMEM) to construct a comprehensive evaluation model to evaluate the ecological benefits of the construction of marine ranching. Based on the survey data of biological resources and environmental factors of marine ranching in ten sea areas of Guangdong Province from 2019 to 2021, we screened out 26 key indicators such as transparency, dissolved oxygen, chlorophyll, primary productivity, planktonic biodiversity, etc., and developed three types of standards as a reference. The results show that the comprehensive evaluation scores of the ecological benefits of marine ranching in Guangdong Province from 2019 to 2021 are 0.588 113, 0.609 307 and 0.521 257, respectively, all of which are higher than the evaluation value of the first-class standard of 0.462 171, revealing that the marine ranching in Guangdong Province have maintained high ecological quality and effectively improved the ecological environment of the sea area. Primary productivity has a high importance in ecological benefit evaluation, and the slight decline in the score in 2021 is mainly due to the rise in inorganic nitrogen content and the decrease in the biodiversity indices of plankton and benthic organisms. It is recommended to further improve the evaluation index system to provide a more scientific method for evaluating the ecological benefits of marine ranching.