Abstract: To detect the overlying strata defects for an urban metro tunnel during construction, the Rayleigh wave method was adopted, in which the signal-noise ratio can be increased by avoiding the peak environmental noise hour and improving the coupling between the detector and the hardened ground surface. Furthermore, the detection data were calculated by the simulated annealing inversion method, which has the advantages of reducing the impacts from the initial model and avoiding the local optimization solution. Engineering practices show that the results of the Rayleigh wave method agree well with those of the low-frequency GPR method/core-drilling method/site construction log in terms of abnormal location.