This paper deals with the main principle of the phase transformation me thod in electromagnetic frequency sounding, which can be realized in the PC-1500 computer.It will remedy the defect that phase cannot be measured dire-ctly, and thus has remarkable practical use. Calculation shows that the trans formed phase curve is consistent with the theoretical phase curve in shape and is characterized by distinet layering and strong capacity for reflecting basement at grent depth. Like the measured phase curve. it can reflect. geoelectric informa tion and characteristics of cross section. On such a basis, a method is proposed which uses phase and amphimde to carry out intergrated frequency sounding interpretation. This method has been employed to interpret frequency sounding conducted in Suibin survey area of Heilongjiang province, and the result is quite in conformity with the drilling and seismic data.