Abstract: In view of problems of big power consumption, inconvenient installation, low sensitivity existed in most of metal detectors in mine because of using analog technology, a design method of an intelligent metal detector was presented. The detector uses digital signal processing method to achieve multi parameter measurement, adopts self-oscillating coil probe to induct metal signal and the induction signal is processed by amplitude amplifying circuit to get amplitude, so as to achieve determination of the metal block size; obtain different frequency from the frequency detection circuit to reach classification of metal types. The experiment results show that the detector can not only detect metal objects size and material effectively and make alarm, but also has stable performance and easy to extend.