The main principle of parking guidance system is to install ultrasonic detector or video detector on the top of each parking space to detect whether there are vehicles parked on the parking space. Then the management system collects all the detection information into the system in real time, and the system feedback the boot information to each pilot indicator signal through the computer in real time. The composition of the parking space guidance system: data acquisition system: install an ultrasonic probe on the top of each parking space (the ultrasonic probe address can be set according to the field situation, starting from No. 1 in order, increasing gradually), Eight ultrasonic probes are connected to a probe controller by RS485 bus. The data processing center can also transmit the information to the acquisition terminal through CAN bus, and then the acquisition terminal can publish the information to the nearby empty parking display screen by wireless or wired way to guide the driver to choose the driving route.