In order to acquaint the application of geological penetrating radar (GPR) in tunnel lining detection elaborately, the tunnel lining model involving diseases (voids, voids filled with water, zone filled with materials and cracks) has been researched with GPR (equipped with a 800MHz antenna). And on the basis of the finite difference time domain method (FDTD), the 2-D simulation model of tunnel lining with different diseases was established with the software GPRMAX2D for further research in 800MHz and 1400MHz antennae. Comparing the GPR images of the test model and the 2-D numerical model with the actual layout settings in the tunnel lining, the following results can be obtained obviously. GPR is impressible to steel, while the lower rebar is difficult to identify for the double-layer rebar; GPR equipped with a 800MHz antenna is appropriate to monitor the void, while the accuracy of the geological radar method is related to the shape, size, depth and water condition of the voids; the accuracy of GPR is almost 50mm for the 800MHz antenna , while it is 20mm for the 1400MHz antenna and cracks can’t be identify with the 800MHz.