Abstract: Aiming at the technical challenges of detecting geological anomalies in the overburden strata and early warning of geological hazards during shield tunnel construction, a field test study of muon imaging technology is carried out in a typical shield tunnel project in Shenzhen. By deploying multiple muon detector arrays and applying an improved iterative density reconstruction algorithm, a high-resolution three-dimensional density structure model of the test area is established, enabling accurate localization of density anomalies in the strata. The results show that: (1) this technology can effectively identify density anomalies in geological bodies with a scale of 1-3 m; (2) in the shield-ahead detection mode, the density inversion sensitivity reaches 2%, allowing clear distinction of the physical boundary between moderately weathered and strongly weathered rock; (3) for a tunnel with a burial depth of 18 m, underground cavities with a width of approximately 4 m located 2-4 m above the tunnel crown can be accurately detected (positioning error <2 m), and the enhanced compactness after grouting reinforcement can be verified.