The invention provides an electric car power system which comprises a battery pack, a battery heater, a battery manager, a distribution box, a motor, a motor controller and an isolation inductor. The battery heater is connected with the battery pack. The battery manager is respectively connected with the battery pack and the battery heater and used for alternately controlling the battery heater to heat the battery pack according to accelerator depth change velocity of an electric car when the temperature of the battery pack is lower than a first heating temperature threshold and the residual electric quantity is higher than a shutdown electric quantity threshold. The distribution box is used for distributing voltage output by the battery pack. The motor controller is connected with the motor and the distribution box and provided with a first input end, a second input end and a pre-charging capacitor. The pre-charging capacitor is connected between the first input end and the second input end and matched with the isolation inductor. The power system is capable of realizing heating and greatly lowering use limitation in a low-temperature environment, high in heating efficiency, low in cost, and highly practical. The invention further provides an electric car battery heating method and an electric car.