Wheelchair is for those who cannot walk independently and need assistances in moving around. Six-wheel Power Wheelchair has great functions, such as large sphere of actions, no movement injuries, great stability, and small radius of gyration. The purpose of this paper is to apply the idea of engineering design method and offer a design theory for chassis mechanism for Six-Wheel Power Wheelchair. Firstly, the evolution of chassis mechanism for wheelchair is discussed and the existing chassis mechanism for wheelchair is analyzed. Based on the knowledge, this paper concludes the fundamental functions and structural characteristics of chassis mechanism for power wheelchair and lists the design requirements. Secondly, applying the creative mechanism design procedures, a new design for chassis mechanism and the Kinematic design for six-wheel power wheelchair are proposed and computerized Finally, using CAE software stimulating the designs, the paper presents the three-dimension graph and prototype of the designs.