A system and a method for detecting irregular bone defects during dental implant osseointegration process. The system comprises a detecting abutment, an ultrasonic driver, a signal receiving and analyzing device. When dental detection is performed, the detecting abutment is disposed on a substrate holder of a dental implant. The ultrasonic driver configures the piezoelectric transducers disposed on the detecting abutment to produce ultrasonic wave and transmits the ultrasonic wave to the contact surface between the dental implant and the alveolus bone. The piezoelectric transducers can receive the reflected wave caused by the each portion of the contact surface reflecting the ultrasonic wave and transform the reflected wave into time domain voltage signal. The signal receiving and analyzing device receives the time domain voltage signal to determine the depth, the severity and the location of the irregular bone defects of the contact surface.