Abstract: In the outdoor parking lot ,parking space detector can be easily interfered by various external factors ,re-sulting in unnecessary errors in parking space detection and incorrect parking management decisions as well as user delay . According to the actual outdoor parking space detection needs and the related detection technology requirement ,this paper presents an approach based on the giant magnetoresistance detection technology ,which achieves vehicle detection by de-tecting the magnetic field change in giant magnetoresistance before and after a vehicle has left .The design is based on gi-ant magnetoresistance detection hardware and software systems ,which provide data for information display and giant magnetoresistance sensitivity adjustment .The test results show that ,compared with other detection techniques ,this parking space detection technology provides higher precision with consistency .