The invention relates to the technical field of voltage sensors, concretely relates to a passive high-temperature voltage sensor utilizing the microwave scattering principle and also a preparation method thereof, and helps to solve the problems that a conventional voltage measuring method has many defects in high-temperature and other severe environments. The passive high-temperature voltage sensor includes a cylindrical pedestal and a sealing membrane. A concave cylindrical cavity is disposed inside the pedestal. Four symmetrical cylinders are disposed in the middle of the concave cylindrical cavity, and the height of each inner cylinder is lower than the upper surface of the concave cylindrical cavity. The upper surface of the pedestal, the inner surface of the concave cylindrical cavity and the upper surface of each inner cylinder are all equipped with metal layers through sputtering. A silk screen on the upper surface of the sealing membrane is provided with a microstrip antenna through sputtering, a grounding plane is disposed on the entire lower surface of the sealing membrane through sputtering, and the lower surface is equipped with a rectangular coupling slit. The pedestal and the sealing membrane are bonded to form a microwave resonant cavity. The passive high-temperature voltage sensor is reasonable in design and high in sensitivity, exhibits great stability, can work for a long period of time in high-temperature, high-voltage and other severe environments, and belongs to a passive high-temperature ceramic voltage sensor for wireless measuring on the basis of microwave scattering.