In order to assimilate and redesign the existing product, a conceptual design driven by function is proposed. Firstly, the behaviors, structures and functions of the product are analyzed in detail. Then bond graph models are used to describe the behaviors which indicate the dynamic performances of the existing product. Secondly, the advantages and disadvantages of the product can be revealed through these dynamic performances which are abstracted by simulating the bond graph models. To catch the intention of the original design, the simulation results are analyzed regarding the system dynamic performances. According to the evolutional routes, several redesign results are obtained by grouping some optimized alternatives. Finally, applying the method to a frictional driver redesign, the control and dynamic performances are both improved, which verifies the validity and practicability of the proposed design method.