Abstract: In view of the current situation that the influence of cycloidal gear tooth profile modification is not considered in the conventional structure design of RV reducer, in order to realize the accurate dynamic structure design of RV reducer, a combined modification method of “negative movement distance-positive equidistance” or “positive movement distance-negative equidistance” of cycloidal gear profile of RV reducer is proposed based on the optimization of load carrying capacity and transmission efficiency. With the maximum load carrying capacity and maximum transmission efficiency as the optimization objectives, the key parameters which have a great influence on them are selected as the design variables, and the influence of tooth profile modification is considered to carry out the multi-objective optimization research on RV reducer. NSGA-Ⅱ algorithm is used to solve the problem, and the optimal parameter scheme of Pareto solution set is determined based on a multi-objective decision method combining TOPSIS and CRITIC. The results show that, compared with the original design, the influence of “negative movement distance-positive equidistance” or “positive movement distance-negative equidistance” modification on the meshing force is smoother than that “negative movement distance-negative equidistance” and “positive movement distance-positive equidistance” modification, and the tooth profile modification design is easier. After optimization, the transmission efficiency of cycloidal pin wheel is increased by 0.96%, the maximum engagement force is reduced by 35.98%, the transmission of the whole machine is more stable, and the dynamic performance of RV reducer is significantly improved.