Different grouping ways and adding orders of the additives of CNG engine oils were used to study the effect of blending technics of compound additives on the performance of CNG engine oils.The experimental results indicate that there is synergistic effect between additives.Different complex agent has considerable effect on engine oil performances,such as viscosity change rate at 100 ℃,coke volume,wear scar diameter,maximum nonseizure load,and it has little effect on viscosity index,pour points,low temperature dynamic viscosity and flash point.By using the optimized adding order of composite agents,such as T106D+T109B+T203,T154B+T161B+T706,L135+L57,the CNG engine oil has the best comprehensive performances.