Owing to inconformity of documents format of design model and construction model, there is a prominent question in the BIM implementation process of facade engineering from the design stage to the construction stage. The data needs to be re-processed and secondary processing during its transformation. To solve this problem, based on the comparative study of IFC standard and STEP standard, this paper establishes the partial mapping relation between them for the common types of curtain wall components, analyzes the similarities and differences in geometric expression, proposes the transformation algorithm of the geometric information of the curtain wall components from IFC format to STEP format, and implements the algorithm by using C++ language. Finally, the correctness and feasibility of the algorithm are verified by the actual case of the curtain wall components.