The present invention discloses a high-efficiency working method for a battery energy storage system at low temperature. In the present invention, combined operation of two kinds of batteries is taken as an example to build an energy storage system framework at low temperature. A lithium iron phosphate battery and a lithium titanate battery are selected for combined operation to achieve complementary advantages of the two kinds of batteries; then, an energy storage system model for combined operation of the two kinds of batteries with the consideration of an impact of temperature on charging/discharging efficiency of the batteries is built; and finally, an optimal dispatching solution for a battery energy storage system composed of the lithium titanate battery and the lithium iron phosphate battery at low temperature is provided. By the above steps, the present invention achieves high-efficiency outputting of electricity of the battery energy storage system at low temperature, achieves complementary advantage of different kinds of batteries, and also ensures low overall cost.