A power system of an electric vehicle, an electric vehicle including the same and a method for heating a battery group of the electric vehicle are provided. The power system comprises: a battery group; a battery heater connected with the battery group; a battery management device connected with the battery group and the battery heater respectively, and configured to control the battery heater to heat the battery group in a running heating mode or in a parking heating mode according to a temperature and a residual electric quantity of the battery group when the temperature of the battery group is lower than a first heating threshold and the residual electric quantity of the battery group is larger than a parking electric quantity threshold; a motor controller connected with a motor and an electric distribution box respectively; and an isolation inductor (L2).