Aiming at the reducer of pure electric vehicle，the gear churning power loss is analyzed based on ParticleWorks software，and the characteristics of gear churning power loss are explored. The orthogonal analysis method is used to analyze the range of the factors affecting the gear oil loss. The main factors affecting the gear churning power loss are speed，gear oil kinematic viscosity，oil depth，number of teeth，tooth width，gear helix angle and pressure angle，and the specific influence sensitivity of each factor is studied. Through ParticleWorks and Romax software，a transmission efficiency analysis model of the reducer is constructed and a transmission efficiency experiment is conducted. Through the comparison and analysis of the experiment and the transmission efficiency simulation，the feasibility and accuracy of the simulation model are verified. A new mean to study the transmission efficiency of the reducer of pure electric vehicle is provided.