The systematic design around the key technology of hightemperature complex permittivity measurement of microwave medium is presented. Dielectric property test at variable temperature is realized by the exact field theory solution. A TM010 mode cylindrical resonant cavity is designed and variabletemperature test system is constructed by using rapid specimen movement platform and induction heating technology. The system can realize the complex permittivity test automatically at 915 MHz and up to 1 400 ℃.For the influence caused by the heating of the test system, the realtime calibration technology is presented to reduce the error from the fluctuation of dielectric property of the fixture. The repeated variabletemperature measurements of the complex permittivity of fused quartz sample are done, and the test data is compared with published data. The results indicate that the test deviations of permittivity and loss tangent at high temperature is less than 2% and 6% respectively.