The utility model discloses a quality detection device for an existing building foundation pile. The quality detection device comprises a hydrophone, an acceleration sensor, pulse discharge source equipment and a data analysis system, the pulse discharge source device is provided with a pulse discharge electrode. A vibration excitation hole and a collection hole are formed in the bearing platformat the top of the foundation pile; wherein the hole bottoms of the excitation hole and the acquisition hole are the top of a foundation pile, the excitation hole is filled with clear water, the pulsedischarge electrode and the hydrophone are both placed in the excitation hole, the acceleration sensor is placed at the hole bottom of the acquisition hole, and the hydrophone and the acceleration sensor are respectively connected with the data analysis system. The foundation pile quality detection device can accurately judge the quality of the foundation pile, and has the advantages of high efficiency and low cost.