The invention provides a power source for an electric vehicle and a power source switching control method and belongs to the field of electric vehicle energy management and control. A system comprises a power battery, an auxiliary energy device and a controller. The controller is used for selecting any one of multiple driving modes to control work of the power battery and the auxiliary energy device, wherein the multiple driving modes comprise a first driving mode and a second driving mode, the controller is configured to select the second driving mode when the remaining electric quantity of the power battery is not larger than a preset calibration value, until the remaining electric quantity of the power battery rises to no lower than a maximum preset value; the controller selects the first driving mode when the remaining electric quantity of the power battery is not lower than the maximum preset value, until the remaining electric quantity of the power battery is reduced to no higher than the preset calibration value, wherein the maximum preset value is larger than the preset calibration value. According to the scheme, the service life of the battery is prolonged, oil consumption is reduced, and the energy saving performance is improved.