Abstract: Mass customization is the trend of modern industry，which not only has the advantage of low cost，but also can meet individual customer requirements．Product configuration is an important method to realize mass customization，and configuration tool is the core of product configuration．GPCT（Generic Product Configuration Tool） is developed by Institue of Design for Innovation，Hebei University of Technology and it is a domain-independent configuration tool．GPCT utilizes UML to represent configuration model and OCL（Object Constraint Language） to represent constraints among product parts．The constraint maintenance and evaluation of GPCT are presented in this paper，taking CNC vertical grinder being as an example，the application of GPCT is introduced．