Functionally graded material(FGM)is a new type of composite material which is widely used,the gears made of FGM have unique properties.In order to research the influence of FGM on the performance of gear lubrication,the transient elastohydrodynamic lubrication of asymmetric polymer gear was analyzed with multiple grid method.The lubrication performances of homogeneous composite material gear and FGM gear were compared,and the gear lubrication law of FGM gear as driving gear and driven gear was analyzed.The effect of thermal properties of FGM on gear lubrication was studied.The results show that FGM can effectively improve gear lubrication performance by reducing the lubrication pressure and increasing the thickness of the lubrication film.It is more favorable for gear lubrication when the FGM gear is used as the driven gear.Thermal elastohydrodynamic lubrication analysis shows that when the FGM gear is used as the driven gear,the lubrication temperature at the engaging-in point is low,while when the FGM gear is used as the driving gear,it is relatively beneficial to thermo-elastohydrodynamic lubrication of the subsequent process.