The composite lining model of railway tunnel is set up and then simulation test is presented by non-contact detection with the simple detection equipment of ground penetrating radar (GPR) to study the main technique parameters of the equipment. The results show that the lining can be detected by the way, and the quality of GPR scan obtained in the simulation test decreases with the detection distance increasing. In the GPR scan obtained when keeping ground-coupled shielding antenna of 400MHz 20cm away from the ground(the distant from the bottom of GPR antenna to the surface of lining specimen), a variety of work conditions that has been preset in the experimental design can be identified, moreover, the location and range of both uncompacted backfill and cavity behind the lining etc. approach those that can be get when the antenna sticking to the lining, thus providing satisfactory qualitative interpretation of GPR scan. In addition, the deviation range of GPR non-contact detection is close to that when the antenna sticking to the lining, thus ensuring the detection value accuracy of lining thickness.