<p>This paper analyzes the impact of land use factors to pollutant distribution in the watershed of Lake Kasumigaura. In the field experiment presented in this paper, two types of optical signals and water quantity were used to estimate the loads of chemical oxygen demand (COD), particulate chemical oxygen demand (P-COD), total nitrogen (TN), nitrate (NO3-N), total phosphorus (TP) and particulate phosphorus (P-P). Artificial neural network (ANN) models are trained to set up the correlations among them. Annual pollutant loads were calculated by the ANN simulation results. Regression analysis was applied to evaluate the impact of different types of land use in different periods to the 6 pollutants respectively. The analysis results showed that paddy fields exert strong positive influence on the load of COD, P-COD, TP and P-P in the flood-irrigation period, and less influence on the load of TN and NO3-N in almost the whole year except the flood-irrigation period. The cropland exerts strong influence on load of TN and NO3-N in the whole year. According to the regression results, pollutant load in unit area in the basin is also estimated.</p>