The ground penetrating radar is usually used to predict tunnel geology. However, it is often disturbed by interfering factors in complex tunnel construction environment; as a result, the prediction accuracy for bad geology can not be guaranteed. Some normal interfering factors, i.e. metal objects around tunnel face, detection surface roughness, cable and transmission line, metal/nonmetal of detection line, water and mud and metal around detection line on tunnel floor, are studied. The expression characteristics on radar image and interpretation of the interfering factors are analyzed. Countermeasures are discussed in terms of relative dielectric constants, direct wave pickup, radar antenna movement, survey line mileage marking, gain control and data processing. The study results can provide reference for similar projects in the future.