Abstract: Since nearly all of the dimension parameters in technological process planning are coupled together,manual method in the process dimension parameter planning(PDPP) is not always efficient and effective.In order to increase design efficiency and effect, an essential mathematic model about PDPP is established,and two basic constraint sets are given.This model is not only helpful to realize the automation and optimization of PDPP,but also useful to verify the correctness of existing PDPP methods and to find better PDPP methods.