Optimum design of rider-bicycle mechanisms is very important for customizing bicycles and plays a crucial role in the improvement of athletes’ performances and in protection of the riders.Since the birth of the first bicycle,people have been keeping optimizing bicycles with respect to physical conditions of human.In modern design,the basic structure of a bicycle has been formulized,while many geographic parameters remain uncertain.In this paper,the bicycle and the human body are considered as a kinematic mechanism,called rider-bicycle mechanism.The optimum design is implemented from the perspective of mechanism.Effort-saving and comfortableness are considered at the same time.The corresponding performance charts are drawn and the relationship between the performances and parameters of seat height,crank length and body parameters are discussed.By using these charts,the optimal design method of bicycle’s parameters for a specified person is then founded.Optimum solutions to get suitable seat height and crank length for a person are obtained accordingly.The research is of significance for customizing bicycles and design of bicycle robot. Optimum design of rider-bicycle mechanisms is very important for customizing bicycles and plays a crucial role in the improvement of athletes’ performances and in protection of the riders.Since the birth of the first bicycle, people have been important optimized bicycles with respect to physical conditions of human.In modern design, the basic structure of a bicycle has been formulized, while many geographic parameters remain uncertain. In this paper, the bicycle and the human body are considered as a kinematic mechanism, called rider-bicycle mechanism. design is implemented from the perspective of mechanism.Effort-saving and comfortableness are considered at the same time. The correspondence performance charts are drawn and the relationship between the performances and parameters of seat height, crank length and body parameters are discussed. By using these charts, the optimal design method of bicycle’s parameters for a specified person is then founded. Optimum solutions to get suitable seat height and crank length for a person are obtained accordingly. The research is of significance for customizing bicycles and design of bicycle robot.