In order to explore the relationship between the feeding quantity, water quality, and plankton in salt-freshwater intensive grass carp farming ponds,this study regularly sampled and investigated the water qualities, amount of feed, and plankton of three brackish water carp farming ponds in Guangzhou Chengyi Aquaculture Co., Ltd. from September 2017 to September 2018. Spearman and Canoco 5.0 were then used to correlate and rank the data. The results showed that the feeding quantity was significantly positively correlated with the total nitrogen concentration of the water, and its correlation coefficient was 0.614 (P<0.05), which was related to water temperature, pH, transparency, dissolved oxygen, nitrite, ammonia nitrogen, total phosphorus and salinity. There is no significant correlation with other water quality indicators. The feed amount and phytoplankton biomass were significantly positively correlated, the correlation coefficient was 0.354 (P<0.05), and the zooplankton biomass was extremely significantly positively correlated, the correlation coefficient was 0.447 (P<0.01). The RDA ranking analysis was performed on the feed quantity and water quality index and plankton biomass. The sorting results showed that the feed quantity and total phosphorus were the key factors affecting zooplankton and phytoplankton biomass, respectively. The multiple regression data model fitted well. The interpretation rate of the prediction model for phytoplankton and zooplankton biomass were 65.4% and 44.8%, respectively. The models were Y1 = 16.07x4 + 13.60x3 + 11.10x2 + 2.22x6-2.20x5-2.06x1-51.57; Y2 = 2243.92x4 + 5.54x3 + 0.90x2 + 0.006x1-57.48. Conclusion: in brackish water intensive grass carp breeding ponds, the feeding quantity has a significant effect on the total nitrogen concentration and phytoplankton in the pond. At the same time, the purification ability of phytoplankton to the pond nitrogen also limits the amount of pond feed. Therefore, the regulation of the feeding quantity in the pond should take the water quality and plankton into consideration.