the dynamic response at multi-points on the shaft of a defective pile under low strain loading condition is investigated theoretically. Three-dimensional axisymmetric continuum soil model is established to simulate the layered pile-soil system considering different types of pile defect. Theoretical solutions are deduced by applying the separate variable method and integral transformation technique. A parametric study is conducted to evaluate the characteristics of the incident velocity wave at multi-points along the pile shaft. Application of dynamic response at multi-points along the shaft of a defective pile in novel pile integrity testing method is discussed afterwards. The results obtained facilitate a new approach for pile integrity testing and provide insights on the dynamic load transform mechanism of the pile foundation under vertical dynamic loads.