Common used system construction method for Rapid Prototyping is encapsulating each machine process into a single service. In order to solve the problems of service description, management, sharing and exchange in Rapid Prototyping industry, an ontology based Knowledge construction method for Rapid Prototyping domain is presented. Firstly, according to the analysis of the representative feature of different Rapid Prototyping schemes, a set of description rules are defined. Then the formal expression of Rapid Prototyping knowledge is represented with the OWL format. And finally, this paper established a sample database which includes 200 RP services descriptions, each correspond to a real...