Abstract: To address the issue of non-uniform meshing gaps and deteriorated sealing caused by thermal deformation in traditional screw rotors, this paper proposes a novel type of equal-clearance meshing rotors in twin-screw vacuum pumps and their design method. Based on the fundamental theory of gear meshing, a smooth rotor profile composed of involute curves and equidistant epicycloids is constructed, along with its conjugate meshing model. Considering thermal and pressure-induced deformation, a design strategy for rotor profiles under operating (thermal) conditions is developed. Through numerical simulation and coupled analysis of the effects of temperature loads and pressure loads on the deformation of the rotor, the velocity field, pressure field and deformation amount inside the twin-screw vacuum pump were obtained. The temperature distribution, gas pressure changes and deformation characteristics of the rotor under actual working conditions are analyzed. Results show that the proposed rotor ensures uniform meshing clearance across all contact regions, significantly improving sealing performance and operational stability. This study provides theoretical and practical guidance for the development of high-performance screw vacuum pumps.