The influence of couple stress parameters on the lubrication performance of dynamically loaded journal bearing was studied numerically based on Reynolds equation.The oil film pressure distribution and axis orbit of a certain type of diesel engine bearing were calculated under the lubrication conditions of Newtonian fluid and couple stress fluid respectively.The numerical results show that compared with Newtonian fluid lubrication,the oil film pressure of the bearing increases under the stress couple fluid lubrication,and the maximum oil film pressure appears in the direction of bearing angle increase with the increase of couple stress parameter.Under the two lubrication conditions,the shape of the axis orbit is similar,but the axis orbit is far away from the center of the bearing under the Newtonian fluid lubrication condition,while under the couple stress fluid lubrication condition,the axis orbit is closer to the center with the increase of parameters,and the minimum oil film thickness increases obviously.The research shows that compared with Newtonian fluid lubrication,couple stress fluid lubrication improves oil film pressure and axis orbit,and the larger couple stress parameter is,the more obvious couple stress effect is.