In periodic signal sampling, equivalent sampling utilizes A/D conversion with lower sampling frequencies to collect high-frequency periodic signals, which to some extent compensates for the low measurement accuracy of undersampling. In order to effectively improve the accuracy and stability of impedance spectrum measurement in high-frequency measurement, a uniform phase sampling impedance spectrum measurement method based on the idea of equivalent sampling was proposed. By utilizing the DAC and ADC modules of a microcontroller with a common clock reference, based on the generation of excitation signals and synchronous acquisition of input and output signals, the excitation signal frequency, acquisition frequency, and signal reconstruction method were reasonably designed to achieve equivalent high-frequency sampling of uniform phase distribution in a single cycle of high-frequency signals. At the same time, a new approach is provided to overcome the problem of difficulty in accurately measuring high-frequency impedance spectrum under conventional A/D conversion speed conditions. From the perspective of error assumptions and fitting algorithms, theoretical analysis proves the reasons for the error reduction of the method. The comparison experiments of two equivalent circuit models of the impedance spectrum measurement. It is shown that the accuracy and stability of impedance measurement are significantly improved in the high frequency band of 20 ~ 100 kHz.