In order to explore the utilization of underground saline water resource in Shiyang River Basin, the soil-water-atmosphere-plant (SWAP) model was calibrated and validated based on field experiments data of saline water irrigation in spring maize field and was used to simulate the long time effect on soil salt dynamic and spring maize yield of saline water irrigation. The results showed that simulated soil water content, soil salinity and spring maize yield agreed well with the measured values. The root mean square error (RMSE) and mean relative error (MRE) were within the allowable error ranges. The SWAP model could be used to simulate saline water irrigation of spring maize after calibration and validation. The long time simulation results indicated that soil salt accumulation was below 2.8 mg/cm3 and spring maize yield was reduced by below 20% under brackish water irrigation of 3.0 mg/cm3 during the simulation period. The soil salt accumulation was above 4.0 mg/cm3 and spring maize yield was reduced by above 38% under brackish water irrigation of 6.0 mg/cm3 during the simulation period. Brackish water irrigation of 3.0 mg/cm3 can be used for irrigation for a relative long duration in the research area, as it has little soil salt accumulation and will not cause significant reduction in spring maize yield. This study has an important significance for saline water irrigation and also guides agricultural production practice.