A load control system includes a power switching device and a control device, wherein the power switching device includes a first power input port, a second power input port and a power output port. The first power input port and the second power input port are electrically connected to a first battery and a second battery respectively, and the power output port is electrically connected to the control device. The power output port receives the power which is input to the first power input port or the second power input port so as to supply the power to the control device. The control device is adapted to control a load to switch and to control the power switching device to utilize the power from the first power input port and the second power input port alternatively, thereby extending the respective usage time of the first battery and the second battery.