Manufacturing Execution System (MES) is one of the crucial technologies that realizing the information integration for the enterprise, and its function modeling is the base of MES design and implementation. Basis on the analysis of the business process in mechanical blanking workshop and the functional requirements of MES system, the IDEF0 method was adopted to construct the function model of MES system oriented to mechanical blanking workshop, and a detailed description of the function modules and their relationship was given, which laid the foundation for the software development of the MES system.