From May to November 2019, the water quality of four freshwater crab culture ponds (T1, T2, T3 and T4) and river supply sources were monitored, and based on nitrogen and phosphorus load and tailwater discharge standard, two models were used to estimate the carrying capacity and the optimal stocking density. The results showed that:During the entire breeding cycle, the TN of the experimental crab ponds within the surface water quality standard of Class Ⅲ, and the TP exceeded the standard in the early stage of aquaculture, and was better than the Class Ⅲ water quality standard at the end; according to the phosphorus emission standard, the carrying capacity of T1, T2, T3 and T4 in a culture cycle is 4 835, 3 894, 5 035 and 4 546 kg, respectively, and the stocking density is 12 012, 12 249, 12 154 and 16 770 ind./hm², respectively; according to the nitrogen emission standard, the carrying capacity of T1, T2, T3 and T4 in a culture cycle is 3 786, 2 999, 3 948 and 3 401 kg, respectively, and the stocking density is 9 406, 9 432, 9 530 and 12 547 ind./hm², respectively, T1, T2, T3 can increase by more than 50%, T4 can only increase by 19.75%. Combined with the actual situation, the culture capacity of river crab in the experimental pond was 2 006-2 598 kg/hm², and the cultivation density was 10 229-13 296 ind./hm²; compared with the phosphorus emission standard, the carrying capacity estimated based on the nitrogen emission standard is lower, which may be related to the excessive nitrogen content in the water supply of the aquaculture pond.