The dielectric properties of rap oil, soybean oil, peanut oil, corn oil and well-distributed oil were studied by the open-ended coaxial probe technology over the frequency range from 200 to 4500MHz and temperature from 20 to 90℃. The reasons why relative dielectric constant and dielectric loss factor changed with frequency and temperature were analyzed. The results indicate that the relative dielectric constant of rap oil was maximal and the dielectric loss factor of which was minimal among five oils at the same frequency. However, the corn oil had minimal relative dielectric constant and maximal dielectric loss factor. The good linear relationships between permittivity and saturated fatty acid and unsaturated fatty acid were found over the frequency from 500 to 4000MHz. The relative dielectric constant decreased linearly with increasing temperature, but the loss factor increased linearly. The permittivity of rap oil was affected obviously by the temperature, while the influence was very small to corn oil. The penetration depths of electromagnetic energy in edible oils decreased with the increase of frequency and temperature. This study was useful to understand the microwave dielectric properties of vegetable oils and to further study the effect of edible oil quality based on the dielectric property. 