Abstract: The grouting fullness degree of concrete bridge is directly related to the bridge safety and life. However, the present methods cannot accurately test the corrugated pipe grouting quality of corrugated pipe. The paper, using the generalized completely matched layer (GPML) as absorbing boundary, based on the finite difference of time domain (FDTD), made 2-D GPR simulations of the grouting hole with same depth and different size in the steel strand, in combination with engineering window verification, summarized the characteristics and rules of duct grouting defects in radar image. The method provides theoretical foundation for detection of grouting fullness degree of corrugated pipe by ground penetrating radar.