An intelligent system is the most effective measure to improve transportation efficiency and urban congestion. The traditional parking space detection technology has some defects, such as low detection accuracy, inconvenient wiring and high cost, which are not conducive to the application of an intelligent detection system. In view of the widespread imbalance between demand and supply of parking spaces, the detection technology based on magnetoresistance sensors has obvious advantages in network, cost, accuracy and operating environment. Therefore, in this paper, a parking space detection system is studied and designed based on the combination of magnetoresistance and microwave radar sensor under the IoT platform, which aims at improving the utilisation rate of parking spaces, meeting the parking space supply, reducing the degree of urban congestion and advancing the management level and efficiency. The effectiveness and practicability of the designed system are verified through data analysis and various functional tests.