The present invention discloses an intruding metal detection method for a supplying-end module of an induction type power supply system having a supplying-end coil controlled by a first driving signal and a second driving signal. The method includes periodically generating a detection signal on the first driving signal and the second driving signal, wherein the detection signal controls the supplying-end coil to resonate and generate a coil signal; setting at least one threshold voltage and comparing a plurality of peak values of the coil signal with the at least one threshold voltage, respectively, to generate a plurality of trigger signals; determining whether to perform a pre-charging procedure according to a resonant frequency of the coil signal; and determining whether there is an intruding metal existing in a power supply range of the induction type power supply system according to the plurality of trigger signals and the resonant frequency.