Abstract: Taking the offshore of Taizhou as the study area, we selected the measured data of representative months in each season and analyzed the distribution pattern of pollutants in different seasons, the data showed that the worst water quality in autumn (October) could account for 45.33% and 33.48% of the model area in terms of inorganic nitrogen and active phosphate respectively. A numerical model was constructed using astronomical tide and wind pressure field as the driving force to simulate the monthly average residual current field in the nearshore area for each representative month of the season. The results showed that the average residual current velocity in the east side of Dachen Island in autumn (October) was 12.09 cm/s, and the pollution level in the nearshore area was more serious when the residual current was southward than when the residual current was northward. In addition, the existence of “residual flow channel” was found in the east side of Dachen Island. When the residual flow was southward flow, the center of the “residual flow channel” was westward, and the east-west gradient of pollutant concentration was larger; when the residual flow was northward flow, the center of the “residual flow channel” was eastward, and the east-west gradient of pollutant concentration was smaller. Based on the analysis of the distribution of residual flow velocity and the distribution characteristics of pollutants in autumn (October) and winter (March), it was found that the trend of pollutant dispersion along the coast increased with the increase of southward residual flow velocity; influenced by the topography, the water quality in the northern part of Taizhou near-shore sea, especially in the northwestern part, was worse in all seasons.