A year-round water circulation model was developed for an office building in Chongqing, China, to investigate the feasibility of antifreeze-free winter operation and cooling tower capacity matching in a dual-season cooling tower coupled with a water-source variable refrigerant flow (WSVRF) system. Experimental validation confirmed that the maximum relative error of the predicted parameters was within 8%. An outlet water temperature of 2 °C was adopted as the operational threshold for the WSVRF system. Based on the validated model, the system operating characteristics and cooling tower capacity matching were systematically investigated under varying winter wet-bulb temperatures and part-load conditions. The results indicate that a cooling tower designed for summer operation can satisfy winter heating requirements at an outdoor wet-bulb temperature of 8.8 °C, with a system coefficient of performance (COP) of 2.84. As the outdoor wet-bulb temperature decreases, the required cooling tower capacity increases nonlinearly. Within the outdoor wet-bulb temperature range of 4.6–8.8 °C, stable operation can be maintained by increasing both the circulating water flow rate and cooling tower capacity, with the system COP ranging from 2.84 to 3.27. However, when the outdoor wet-bulb temperature falls below 4.6 °C, the system can no longer maintain the required outlet water temperature of 2 °C due to the cooling tower practical capacity limit. Beyond this point, further increases in cooling tower capacity yield only marginal improvements in outlet water temperature while reducing economic performance. Therefore, auxiliary heating becomes necessary to ensure reliable and energy-efficient operation. This study provides theoretical and practical guidance for the design and operation of dual-season cooling tower systems in hot-summer and cold-winter regions.