A method is used for a supplying-end module of an induction type power supply system, for adjusting output power of the induction type power supply system. The method includes driving a supplying-end coil of the supplying-end module by using a first driving signal and a second driving signal, and setting a phase shift quantity between the first driving signal and the second driving signal; detecting a coil signal of the supplying-end coil to determine a peak location of the coil signal; determining a peak deviation rate of the peak location according to a starting point of a period of the second driving signal and a zero load point; and adjusting the phase shift quantity according to the peak deviation rate, in order to adjust the output power.