An approach to automatically converting a design feature model to an analysis feature model for downstream finite element analysis is proposed. The analysis feature model is a mixed-dimensional model with shell features representing thin regions and solid features representing thick regions. In the approach, the design feature model is first decomposed into a set of remnants of additive features, each of which represents part of an additive feature’s volume that remain in the final volume of the design model. The remnant of each additive feature is then decomposed into swept bodies and non-swept bodies. After that, the thin regions of each swept body are effectively recognized based on its sketch information. These detected thin regions can be wrongly recognized, which, together with potentially missing ones are thus detected and corrected by a synthesization process. Finally, the analysis features and their relative interfaces are generated, which ultimately gives the corresponding analysis feature model to the input design feature model. Experimental results are also shown to demonstrate the proposed method’s effectiveness.