Based on the needs of water resources management in the Tarim River Basin, the relationship between surface water and groundwater conversion was revealed to better exert the overall function of regional water resources. Using the HSPF-MODFLOW model, daily runoff process simulation was carried out in the basin, and the Nash coefficient E_ns, the deterministic coefficient R² and the root mean square error σ were selected to determine the simulation results. Under changing conditions, the atmospheric precipitation-surface water-groundwater conversion law was clarified. The results show that the simulated Nash coefficients of surface water in the calibration period and the verification period were both greater than 0. 7, and the simulation results of long-term continuous runoff were good as well. The simulated variation of groundwater level with the recharged quantity was basically consistent with the measured value. With the continuation of intermittent ecological water conveyance downstream of the main stream, the groundwater level in the lower reaches has risen remarkably, but the lower section of the ecological corridor has a small uplift. In 2004, the average groundwater depth of downstream groundwater was about 6. 21 m, and it was expected to reach 4. 73 m in the planning year. The coupled model can accurately simulate the process of surface runoff and groundwater dynamic change, which is significant for the joint evaluation and comprehensive management of water resources.