The invention discloses a system and a method for acquiring material dielectric constants in a high temperature environment. The method comprises the steps of: S1, calibrating the system for acquiring material dielectric constants in the high temperature environment without starting a high-temperature box, and acquiring direct-connection S parameters between receiving and transmitting antennas in a normal temperature environment; S2, placing a material to be tested in a measuring clamp and heating the material by using the high-temperature box so that the material to be tested is in the high temperature environment, measuring S parameters of the material to be tested in the high temperature environment, and correcting high temperature error of the S parameters of the material to be tested in the high temperature environment according to the direct-connection S parameters in the normal temperature environment; S3, performing phase correction on the S parameters of the material to be tested after correcting the high temperature error to obtain S parameters of the material to be tested after correcting the transmission phase; S4, and calculating and acquiring dielectric constants of the material to be tested according to the S parameters of the material to be tested after correcting the transmission phase. The technical scheme provided by the invention can acquire accurate and reliable material dielectric constants within a temperature range from room temperature to 1500 DEG C.