Three kinds of scheme of single stage,twin-stage and four-stage transmissions are designed for a light pure electric bus,and then the parameters matching of the power assembly is carried out. The vehicle models are built in Cruise,and then the simulation of the dynamic and economic performance of the three schemes is carried out,the simulation results show that the dynamic and economy performance of multi-gear transmissions are higher than that of single reducer. Because there is no significant improvement of the dynamic and economy performance between the four-stage transmission and twin-stage transmission,in addition,the increase of gear will lead to the problem of shifting difficulties and manufacturing cost increasing,etc. So the twin-stage transmission has a relatively comprehensive advantage.