An energy storage system and a thermal management method therefor are provided. The method is performed by a smart battery thermal management unit in the energy storage system. In the method, a charging-discharging current in a next preset time period, a current parameter of a battery cell, a predicted ambient temperature in the next preset time period, and a refrigerant returning temperature are acquired. A heat dissipation strategy with minimum total power consumption in the next preset time period is determined based on the charging-discharging current, the current parameter of the battery cell, the predicted ambient temperature, the refrigerant returning temperature and power consumption of the cooling system. The cooling system is controlled based on the heat dissipation strategy with minimum total power consumption, to cool the energy storage system.