Abstract: A dimming switch device includes a key switch having a switching element controlled to be open-circuit or closed-circuit, a rectifying diode to rectify input AC voltages according to the state of the switching element, a power state coupling circuit, a controller, and a driving circuit. The key switch and the power state coupling circuit together generate a signal to inform the controller whether the switching element is open-circuit or closed-circuit through a pair of power lines that transmit both the signal and the power required by the dimming switch device and an electric load driven by the driving circuit. Methods for determining user operation events over the dimming switch device are also provided as routines like: reset, one-click, N-click, so that a lamp load can be turned on and off and adjust brightness according to the user operation events.