Abstract: Combined with the TGP206 seismic reflection method and engineering geological survey, the synthetic geological prediction based on GPR is carried out for a super long tunnel. Using the finite-difference time-domain (FDTD) method, the forward simulation synthesized maps of typical defective geologies in front of the tunnel face are obtained, which are the basis for the interpretation of actual detection images of GPR. Long-distance prediction 100 m ahead of the tunnel face is carried out by means of the TGP206 geological prediction system, when approaching the defective geologies, more accurate short-range prediction 20~30 m ahead of the tunnel face is carried out through the geological radar. The proposed method is applied in the prediction of fault fracture zone and water-rich zone in practical engineering. The predicted results are accurate and can effectively guide the tunnel construction. The synthetic advanced geological prediction method can provide a reference for similar projects.