In addressing the limitations of the existing equal cross-section scroll profile, particularly with regard to the number of turns and the extensive leakage line, the theory of three base circle involute scroll profiles was proposed, and a new variable-section scroll profile was constructed using this theory. At the same time, current variable-section profile optimization designs have a key limitation, that is, they focus solely on volumetric performance as the optimization objective, and fail to consider the mechanical properties of the profile, a multi-objective optimization design method that comprehensively considers both volumetric performance and mechanical properties was proposed. Specifically, the key indicator of volumetric performance, the compression ratio, and the important indicator of mechanical properties, the axial gas force, were taken as optimization objectives, and a genetic algorithm was used for multi-objective optimization. The research results show that both optimized indicators have significant changes compared to those before optimization. The compression ratio increased by 19.61%, and the axial gas force significantly decreased, indicating that the proposed optimization method can obtain a variable-section profile with superior comprehensive performance. Moreover, this method also provides a reference for the optimization of other types of variable-section profiles.