Abstract: The field hydrology model(DRAINMOD), recommended by the NRCS of American, can be used to analyze the hydraulic capacity of wastewater land treatment systems. But the wastewater irrigation amount is calculated based on the soil infiltration, evaporation and drainage from the hydraulic aspect, which does not consider wastewater treatment effect. The solute concentrations of drainage outflow under different hydraulic loading rates predicted by DRAINMOD was analyzed using the solute transport model. The proposed method was applied to a case study in Xi'an, China. Results show that when the hydraulic capacity of a wastewater land treatment system increase with the decrease of the drain space, the treatment effect will be worse. This model is also used to determine the required pretreatment level of wastewater under different water quality standards in the wastewater land treatment system.