Ground subsidence is a typical underground disease that severely affects the operational safety of cities and the safety of people’s lives. Ground subsidence often develops from underground cavities. Therefore, to prevent the occurrence of ground subsidence, a method that can effectively detect underground cavities is needed. This paper conducts detection of underground cavities based on the Superconducting Quantum Interference Device (SQUID). Firstly, an underground cavity model is established in COMSOL, and the magnetic anomalies of the cavity are simulated. Secondly, an underground cavity detection experiment is conducted. The experiment is divided into two parts: Experiment 1 is an anomaly-free ground experiment, and Experiment 2 is a cavity detection experiment. The result of Experiment 1, the result of Experiment 2, and the simulation are then compared. The experimental results are generally consistent with the simulation results in terms of trends. At the same time, the feasibility of detecting magnetic anomalies in underground cavities is demonstrated. This provides a foundation for the inversion and positioning of underground cavities based on magnetic anomalies.