Abstract: The impedance spectroscopy might be used to investigate the dynamics behavior of bound or mobile charge in the bulk or interfacial regions of any kind of solid or liquid materials.The technique of impedance was introduced firstly.The impedance spectroscopy of sandstone was tested at different physical states by CHI600A electrochemical workstation.It was shown that the impedance spectroscopy of rock included four parts.To analyze the Nyquist chart of rock and the data of impedance spectroscopy of porous medium,the variation of AC impedance spectroscopy(ACIS) revealed the variation of the different inner structure of rock.The high frequency part of ACIS was one-stage capacity reactance arc which reflected the volume characteristics of rock,including the size and connection condition of rock inner pore and their uniformity.The parameters of rock microstructure in the high frequency part of ACIS were selected.The relation of the parameters of the high frequency part of ACIS and rock microstructure was established.It was a new idea to test the rock microstructure.