The special metal detector for grave robbery uses the principle of electromagnetic induction to generate a rapidly changing magnetic field through a coil with alternating current. This magnetic field can induce eddy currents in metal objects. Eddy current will produce magnetic field, which will affect the original magnetic field and make the special metal detector for grave robbery sound. The accuracy and reliability of the metal detector for grave robbery depends on the stability of the frequency of the electromagnetic transmitter, which generally uses the working frequency of 80 ~ 800 kHz. The lower the working frequency, the better the detection performance of iron; The higher the working frequency, the better the detection performance of high carbon steel. The sensitivity of the detector decreases with the increase of the detection range, and the magnitude of the induced signal depends on the size and conductivity of the metal particles.