Disclosed is a serial-connected alternating current power supply system comprising two alternating current power supplies and loads thereof serial-connected in an alternating current circuit. The alternating current power supplies comprise corresponding AC/DC converters, voltage detection circuits, dummy load control circuits, and bypass dummy loads. When a change occurs in any load that causes a change to occur in an input voltage of the alternating current circuit, the dummy load control circuits automatically control or regulate the bypass dummy loads and automatically balance input voltages of the power supplies via input voltage regulating ranges of the alternating current power supplies themselves, thus allowing the two serial-connected power supplies to always maintain respective normal outputs. The present invention completely solves the shortcoming of insufficient power supply with a single live wire of an electronic switch and is broadly applicable in the field of lighting control for smart homes.