An integrated system of geometric modeling and machining simulation of end mills is presented for supporting end mill’s cutting analysis, structural optimization and digital manufacturing. In order to obtain accurate structural models, the main elements and detail features of end mills are modeled precisely, based on modular design and parametric design methodology. Through integrates 2D tool path and 3D virtual machining simulation seamlessly, a comprehensive simulation platform is constructed. To ensure the accuracy of manufacturing simulation model, the machining simulation model is compared to ideal design model. The results verify the correctness and rationality of the geometric modeling and machining simulation. NC codes generated by machining simulation can be output to tool grinder, supporting digital manufacturing of end mills.