Abstract: In order to decrease the energy consumption of the traditional AC contactor effectively, this paper presents a design of intelligent energy-saving controller for AC contactor based on MSP430F169. The controller adopts pulse width modulation (PWM) method to control MOSFET on and off for regulating the voltage on the AC contactor’s coil, which can accomplish high-voltage excitation and low-voltage maintenance of the coil and the energy consumption of AC contactor will be reduced greatly. On the basis of RS485 interface, the controller increases USB interface to realize two-way communication with PC. Moreover, the controller also has the intelligent functions such as online settings, parameters display on LCD and voltage measuring of coil and so on. The results of experiments show that the energy-saving effect of AC contactor is excellent and about more than 96% of energy is saved.