Abstract: Planetary gear, as primary transmission system and the secondary system cycloidal pinwheel, together form the RV reducer．During assembly process of complete reducer, deviation source of each component directly affects transmission accuracy through transmission of deviation value．The focus of this study was on influence of deviation transmission mechanism on transmission accuracy of RV reducer of slot flip throwing machine during assembly process．Based on the Monte Carlo method, assembly deviation statistics of the RV-40E reducer and entire machine were solved, and conclusion was drawn that the second level transmission deviation value has the greatest impact on transmission of reducer's overall deviation．This has important engineering practical significance for promoting research and development of reducers and development of organic fertilizer tipping systems in China．