Rapid urbanization in China leads to serious eutrophication problem as extra nitrogen and phosphorus input urban watersheds. Therefore, it is important to trace nitrogen and phosphorus pollution to control and manage water quality in those areas. In this study, the spatial and temporal distribution of nitrogen and phosphorus were analyzed in Xiaojia River watershed which located at an urban area of Ningbo in the Yangtze River Delta. The influence factors of eutrophication problem were also analyzed. Water samples for nitrogen and phosphorus were collected in summer and winter of 2017 based on land-use type and topographic features. The results showed that the concentration of nitrogen and phosphorus varied at large scales:ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), nitrite nitrogen (NO₂^--N), total nitrogen (TN), total phosphorus (TP) and chlorophyll-a (Chl.a) concentrations were 0.63-3.25 mg/L, 0.52-3.75 mg/L, 0.02-0.22 mg/L, 1.61-12.86 mg/L, 0.02-0.74 mg/L and 0.60-60.57 μg/L, respectively. Large spatial and seasonal variations were found across the sampling sites in the studied watershed. We use the synthetic eutrophication index EI to assess eutrophication level in watershed, and the results showed that the watershed has eutrophication level of poor to medium. The Spearman correlation statistics for the 100 m buffer area showed that the concentration of NH₄⁺-N (R²=0.639, P<0.05), NO₂^--N (R²=0.591, P<0.05), TN (R²=0.674, P<0.01) and DO (R²=-0.660, P<0.01) were positively correlated with construction land ratio. The wetland was significantly positive correlated to DO (R²=0.528, P<0.05). In the catchment area, the forest ratio was negatively correlated with NH₄⁺-N (R²=-0.594, P<0.05), NO₂^--N (R²=-0.736, P<0.01), TP (R²=-0.663, P<0.01), PO₄^3--P (R²=-0.533, P<0.05), COD (R²=-0.659, P<0.01), Chl.a (R²=-0.531, P<0.05). But it was positively correlated with DO (R²=0.756, P<0.01) and Correlation statistics and RDA sequencing analysis showed that the principle sources of nitrogen and phosphorus pollution in Xiaojia River watershed were strongly associated with urban non-point source and some point source that exist along the river. Therefore, restricting the construction land scale and pollutant discharge are the main routes to decrease nitrogen and phosphorus pollution in 100 m buffer area. However, enlarge the forest ratio is important for controlling nitrogen and phosphorus pollution in the catchment area.