For the purpose to develop the weather generator in SWAT model, a method to estimate daily solar radiation was proposed on the basis of relationship between sunshine duration and solar radiation, and a procedure was proposed to calculate daily dew temperature from daily air temperature and humidity. The interpolation method was used to make the soil grain size conversion, and the soil water characteristics were estimated by the SPAW program to build up soil property database. Finally, the SWAT model was applied in the hydrologic simulation in upper stream of the Cao River Basin. The monthly efficiency coefficient is greater than 0.89 and the coefficient of determination is greater than 0.95, so the simulation is successful. The result shows that the SWAT model can be used in hydrologic simulation in case of absence of detailed weather and soil data.