Abstract: GPR (ground penetrating radar) technique has the advantages of quick, accurateness and real-time processing/display especially available to collect continuously high-resolution sections of underground pile. Investigating quantitatively and qualitatively the relationship of GPR information to the pile integrity including shape and length of macadam, powder spray pile and bottom expansion pile, a complete set of applications of GPR technique and relevant operation procedures was and proposed as supplement to the conventional detection procedure. The characteristics of testing and detection technique were discussed and evaluated under different conditions, with proposed method exemplified to verify its feasibility and usefulness. The results show that GPR technique will provide a big amount of detailed reliable information to the engineering quality inspection of underground piles of composite foundation structures.