A method is provided for controlling a vehicle-mounted charger. The method includes: obtaining a first total charging time for controlling the H bridge in a first manner, a second total charging time for controlling the H bridge in a second manner, a first total discharging time for controlling the H bridge in the first manner and a second total discharging time for controlling the H bridge in the second manner; calculating a first total working time in the first manner and a second total working time in the second manner; and selecting a manner according to a relation between the first total working time and the second total working time to perform a temperature balanced control over the first to fourth switch transistor if the vehicle-mounted charger charges the power battery, or if the power battery discharges via the vehicle-mounted charger.