Water bodies are essential components of many urban parks, with varying water surface ratios affecting the parks' benefits. Therefore, a suitable water surface ratio is crucial for the sustainable development of urban parks. However, research on this aspect remains relatively scarce. In this study, we aimed to explore the suitable water surface ratio for urban parks to enhance integrated benefits. Taking Nanjing Dashengguan Park as an example, different water surface ratios were simulated using the ArcGIS 10.8 platform. Ecological benefits, social benefits, and integrated eco-social benefits models were constructed to measure the benefits of parks with different water surface ratios and to determine the optimal water surface ratio that maximizes comprehensive benefits. The results show that: (1) The water surface ratio significantly influences park benefits. Increasing the water surface ratio improves ecological benefits but reduces social benefits, with integrated eco-social benefits first rising and then declining; (2) A 33% water surface ratio maximizes the integrated benefits of Dashengguan Park, representing the optimal ratio. The method for planning the suitable water surface ratio proposed in this study provides valuable references for the planning and construction of urban parks.