The efficiency of the steel pushing V belt continuously variable transmission is an important factor for weighing CVT performance.Based on the mechanical analysis,by synthetically considering the effect of the viscosity lubricant on the power loss of CVT, the calculation formulae of efficiency have been found. The calculation simulationof efficiency is done, qetting two efficiency trend charts. One is efficiency with torque and rotational speed variation .The other is efficienccy with torque and ratio variation. The two charts have a guiding function in formulating matching and a control strategy and in an efficiency experiment.