To meet the needs of customer parking guidance in large parking lots of shopping malls, this paper introduces a design of a parking lot guidance system based on single chip microcomputer. It uses AT89C52 microcontroller as the main control chip, uses HC-SR04 ultrasonic sensor to collect parking information, and transmits data to the computer through serial port and nRF24L01 wireless transmission module. The host computer software is written by VB and receives data by MSComm control. The experiment shows that the system has the advantages of low cost， low power consumption and high reliability as well as certain practicability.