Gears are widely used to transmit power between two parallel shafts. Study on the lubricant film which is formed between the engaged teeth of pinion and gear is of high importance in predicting the performance of the power transmission system as well as surface failure and wear. Gear surfaces in comparison to rolling element bearings have a higher surface roughness and thus considering the surface roughness is important in gear analysis. In this research, the performance of a pinion-gear system operating under mixed-elastohydrodynamic lubrication is being investigated using load-sharing concept. The contacting asperities might experience elastic, elasto-plastic or fully plastic contact. The engagement of pinion and gear for each point along the line of action is replaced with contact of two cylinders. The radii of these cylinders as well as the exerted load vary along the line of action. Using load-sharing concept, the proposed model can predict the lubricant film thickness, friction coefficient, and portion of the total load that is carried by asperities as well as lubricant film. The predicted results are verified by comparison to other available methods which are published in the literature.