Reclaimed water is key to balancing urban water shortages and green space irrigation. However, improper use risks excessive phosphorus pollution, which demands scientific assessment. This study relies on the field planting measured data from Zhangjiakou City, China, a typical arid and semi-arid region, to conduct high-precision parameter calibration and validation for the HYDRUS-2D model. A comprehensive evaluation of water flow characteristics and phosphorus fate was performed using this optimization model, based on the input of 15 combinations of varying irrigation intensities and phosphorus application rates. Research results show that longterm single reclaimed water irrigation (RI) risks excessive phosphorus accumulation and potential groundwater pollution, whereas mixed irrigation with reclaimed water and clear water (MI) better promotes phosphorus retention and morphological transformation in the soil profile. Parameter calibration and validation have shown that the HYDRUS-2D model has high reliability in simulating soil hydrodynamics processes and phosphorus migration. The optimal irrigated water with phosphorus of 1.00 mg/L and an annual quota of 227.94 mm, could balance groundwater protection and efficient reclaimed water use. This mechanism significantly reduces cumulative drainage by 16.96 % while only slightly decreasing plant root water absorption by 5.37 %, thus improving water use efficiency. These results provide a guiding basis for sewage green treatment and urban sustainable irrigation on turfgrass in arid and semi-arid cities.