Abstract: The radome must maintain superior electrical properties under combined mechanical and themal loading conditions. In this paper, a variable-thickness radome operating in the millimeter band is designed. This radome uses homogeneous ceramics as the base material, takes the wave-transmitting and aiming characteristics as the optimization objectives, and the insertion phase shift of the radome wall as the optimization parameter. Through the ray-tracing method, the design of the variable thickness of the radome wall is carried out, and the design of the variable-thickness radome with an average thickness of 6.4 mm is completed. The three-dimensional electromagnetic field simulation software is used to verify the performance of the radome, and high wave-transmitting and aiming characteristics are achieved in the millimeter band. At the same time, compared with a variable-wall-thickness composite ceramic radome with an average wall thickness of 4.25 mm and two homogeneous ceramic radomes with equal wall thickness, this design has performance advantages . In addition, this paper also presents an analysis of the influence of the high-temperature environment on the performance of the radome. The test results indicate that the power transmission coefficient and aiming error characteristics are consistent with the design values. This paper provides a high-performance solution for the design of radome under the condition of combined mechanical and themal loading.