Abstract: Based on the couple stress fluid model and Elrod's cavitation algorithm, a numerical model of the thermo-hydrodynamic lubrication of journal bearings is built up. The midified Reynolds equation and the midified energy equation of oil film together with the heat transfer equation of the bush are solved. The effects of couple stress on the thermohydrodynamic performance of a finite journal bearing are investigated. It is found that the couple stress fluids, compared with the Newtonian fluids, not only produce an obvious increase in load capacity and a decrease in friction coefficient, but also yield a change in the side leakage flow and the temperature field of oil and bush.