Abstract: The tunnel lining cavity is a common defect in tunnel engineering, which is harmful to the operation safety of the tunnel. The application effects of GPR in detection of railway tunnel lining cavity are studied through the combining model tests and field solid tests. The edges, upper interfaces and ranges of 27 unreinforced inclined cavity models, unreinforced horizontal cavity models and reinforced horizontal cavity models are detected by GPR, and compared with the actual sizes of the cavity in the model. The results show that the radar detection images of the unreinforced inclined cavity model have high discrimination, complete cavity shape, clear cavity edge and upper interface structure boundary, accurate cavity range and error of -0.4~0.5 cm. The starting point of the unreinforced horizontal cavity model is clearly and accurately visible, the radar image interface on the upper surface of the cavity is clear, and the error is -0.4~1.3 cm, but the lower surface of the cavity can only qualitatively explain the approximate depth range of the cavity. The horizontal cavity with reinforcement has complete interface shape and clear structural boundary. The research results may provide reference for the quality inspection of tunnel linings by GPR in the future.