In order to optimize the lower power current-mode signaling (CMS) circuit, we offered a top-down methodology to optimize the power of a dynamic overdriving CMS circuit. First, we molded the CMS scheme using a behavioral model-switched current source, which helps us determine the branch current quickly. Under the help of Matlab, we can determine the optimized branch currents, making the average power of the CMS scheme lowest. To get the accurate dimensions of MOSFETs quickly, a new design method of 2I_D/g_m methodology is introduced. Moreover the detail analysis shows that the 2I_D/g_m methodology is both practical and scientific. The simulation results using initial values calculated by this methodology are very close to the specs, demonstrating the top-down methodology improving the design efficiency of the dynamic overdriving CMS-circuit.