Abstract: Aimed at a convenient method to calculate gear-meshing power losses, based on the theory of the EHL and the minimum elastic potential energy principle, a gear meshing loss calculation model was proposed for high speed involute helical gear. Considering the simulation result and experimental curves of the rig test with sole parameter, the principle was revealed about the effect the parameters of gearbox on the transmission efficiency. A prediction model was proposed for the helical gear-meshing efficiency under high-speed and heavy-load work condition. The results from the analytical model show that the gear-meshing power losses are liner to the gear torque and nonliner to the gear speed when they are logged; the data get from analytical model are accord with the original data; the efficiency of gearbox under high-speed and heavy-load can be calculated quickly, and the calculation results are in the acceptability range.