In order to understand the composition and structure of suspended particulate matter (SS) in the water of grass carp ponds and its changing characteristics, a static sedimentation method was adopted for the sedimentation treatment of grass carp aquaculture water, and a laser particle size analyzer was used to investigate the changes in the particle size distribution (PSD) of suspended particulate matter before and after the sedimentation of aquaculture water, to determine the changes in the water quality indexes before and after the sedimentation, and to analyze the characteristics of the sedimentation of the suspended particulate matter. The results showed that the SS produced in the aquaculture water of grass carp ponds gradually decreased with time,the concentration of SS in the water decreased significantly (P < 0.05) after 30 min, and the SS in the upper water could be reduced by more than 60% after 150 min; After 30 min of standing, the PSD of SS in the upper and lower water bodies showed significant differences (P < 0.05), SS with particle sizes larger than 100 μm were deposited at the bottom, and SS in the upper water body tended to be distributed in small particle sizes as a whole; with the prolongation of the settling time, the specific surface area of the SS in the water body increased gradually, particulate inorganic matter (PIM) had a faster settling rate than particulate organic matter (POM), and after 150 min After 150 min, the main component of SS in the water body was POM; SS had an influential effect on the water quality, TN and TP mass concentration  in the water body decreased with the prolongation of settling time (P < 0.05) and stabilized after 120 min. The results of the study further understand the settling characteristics of suspended particulate matter in the aquaculture water body of grass carp aquaculture ponds, and provide a certain theoretical basis for the regulation of suspended particulate matter in the aquaculture water body of grass carp aquaculture ponds.