Abstract: Thermal elasto-hydrodynamic coupling characteristics of the main bearing including the layer of functionally graded materials（FGM）were investigated on a diesel engine. The transient Reynolds equation,heat conduction equation and thermal elastic equation were discretized based on the cell-vertex finite volume method,and then the algebraic equations were calculated by the multigrid method. The two dimensional energy equation was discretized by the finite difference method. Then the oil film lubrication characteristics and the thermal elastic results of the bearing bush were obtained. The results show that the functionally graded layer can effectively alleviate the stress mutation near the material interface. With the increase of material index,the material parameters of functional gradient layer change more evenly,which results in the decreasing of the maximum oil film pressure,oil temperature,and the stress near the material interface to a certain extent.