The scheme design process for four-axis machining centers is proposed based on analysis of main kinematic chain, topological and tool changing motion characteristics of machine tool in this paper. All possible kinematic schemes of four-axis machining centers with tool change mechanisms up to eight links are generated. And the number of that is 74 with mechanisms of tree graph considered only. Further more, several schemes can be derived from each one of schemes with characteristics of tool change directions and types of tool magazine considered. The results of this work provide references for new multi-axis machining center's development and layout design.