The combination of antenna array detection method of ground penetrating radar was put forward to solve the actual engineering problem that is difficult to monitor the integrity of the flexural pile composite foundation. The experiments of the lengths and defects of six tamping soil cement piles have shown that the maximum average relative error of pile lengths is 5.10% and the relative error of the pile position of defects is 5.45%. The results have indicated that there is enough reliability to determine the pile integrity by using the GPR method,which can meet the engineering needs. Furthermore, the age of cement, the ratio between soil and cement, moisture content were studied, and corresponding proposals for actual projects were presented.