Abstract: In the report, a design scheme of automatic control system for pet feeder based on AT89 S52 microcontroller was proposed. The design methods of software and hardware of the system were introduced in detail. The system hardware design includes speech output circuit, food supply control circuit, infrared induction water supply circuit and key-press adjustment circuit and so on; the system software is mainly composed of main program, feeding control subroutine and automatic water supply control subroutine. The results showed that the pet feeder can realize the functions of regular feeding and automatic water supply for pets, and which can flexibly adjust the feeding time, quantity of food supply and the sensing range of automatic water supply according to different pets, and achieve the automatic control for pet feeder.