In response to the drawbacks of complex profile design and difficult processing caused by the introduction of high-order curves in the construction process of existing variable cross-section scroll profiles, this paper used the base circle involute with stable performance and easy processing characteristics to construct a new type of variable cross-section scroll profile, and established the basic geometric theory of the profile. To quantitatively measure the performance of this profile, an important indicator in volumetric performance, namely compression ratio, and two key indicators in mechanical performance, namely axial gas force and tangential gas force, were introduced, and their performances were evaluated. The results show that, under the same basic parameters, the newly constructed variable cross-section profile has more advantages in terms of volumetric and mechanical properties compared to the traditional variable cross-section profile combination of base circle involute, high-order curve and base circle involute. The compression ratio is increased by 25.81%, and the axial and tangential gas forces it bears are significantly reduced, especially the maximum axial gas force is reduced by 17.28% and the maximum tangential gas force is reduced by 27.15%. The research results provide a certain references for the design of variable cross-section profiles without introducing high-order curves.