As shown in Figure 4, the mean maximum value of DIRTMX of surface sediment of seven urban land types in the Licun River basin is 28.84 kg/km for URLD, and the minimum value is 6.09 kg/km for UINS. The mean maximum value of TNCONC is 83.29 × 10³ mg/kg for URHD, and the minimum value is 15.32 × 10³ mg/kg for UINS. The maximum mean value of TNO3CONC is 0.53 × 10³ mg/kg for UINS, and the minimum value is 0.14 × 10³ mg/kg for UINS. The maximum mean value of TPCONC is 7.96 × 10³ mg/kg for URHD, and the minimum value is 1.43 × 10³ mg/kg for URMD. The initial values for the key parameters of the established SWAT model urban database are shown in Table 3. The measured values of DIRTMX, TNCONC, TNO3CONC, and TPCONC of the SWAT model urban database in the Licun River basin differ significantly from the reference values provided by the SWAT model. This result is because the default parameter values of the SWAT model urban database are based on relevant studies in urban construction areas in the United States, which differ significantly from the current situation of urban nonpoint source pollution in China. Therefore, when constructing the SWAT model to study urban nonpoint source pollution in the basin, the parameter values in the SWAT model urban database must be modified according to local characteristics.