Abstract: Aimed at the 3D modeling problems in end mill design due to its complicated structure, varieties of size, a complete solution was suggested based on the differential geometric curve and surface theory and the relative motion between grinding wheel and cutting tool. Mathematical equations including arbitrary pitch groove section line, equal helix angle, equivalent lead spiral blade line and Gash surface were established.Furthermore, a solid parametric design software of end mill was developed.Rapid generation of the 3D end mill model and the information interaction with CAE software were achieved.Example results show that the established mathematical model can express the end mill rapidly and accurately, efficiency and accuracy for end mill design are improved greatly.