Abstract: As an electric property of rocks, dielectric constant has been used in recent years as a new parameter in well logging. Essentially different from resistivity, dielectric constant is a measure of polarizability of rocks and its effect on the electric field is manifest only at the frequency of over dpzens of mega-hertz. For this reason, high frequency is used in studying the dielectric constant. With the help of condenser and high-frequency electromagnetic wave, the relationship between the dielectric constant of rocks on the one hand and mineral content and distribution, water content, salinity, temperature and mud content of rocks on the other in a 60 megacycle field is determined, together with the character of frequency dispersion of the dielectric constant of rocks, oil and water etc. in a field with frequency ranging from 5 kilocycle to 250 megacycle. With the relationship thus ascertained, the dielectric property of rocks in a high-frequency field is known, thus providing a reliable theoretical basis for interpretation of phase dielectric logs, designing of instruments and evaluation of high-frequency electromagnetic logging.