The invention discloses a thermal compensation system for an electric vehicle battery pack. The thermal compensation system comprises a battery box, battery cells and a temperature equalizing device, wherein the temperature equalizing device is used for thermal compensation of the battery cells, and comprises composite phase change material boards, a battery management system, a temperature sensor and a cooling fan; a composite phase change material board is clamped between two adjacent battery cells, and the outer surfaces of the outermost battery cells are coated with composite phase change material boards respectively. As the properties of a phase change material are utilized by the thermal compensation system, the heat absorption of the battery pack is realized, the normal working condition of the battery pack is guaranteed, the service lives of the battery cells are improved, the structure is simple, the maintenance and repair are convenient, and the reliability is higher.