Abstract: Using CFD software, and considering the SST turbulence calculation model and N-S equation for rotation property of viscous fluid, the oil film pressure distribution of three-lobe journal bearing was studied so as to analyze its influence on the stability of steam turbine rotors, and to carry out a comparative analysis of the oil film pressure distribution among the three-lobe journal bearing, the cylindrical bearing and the elliptical bearing. Results show that, under the same conditions of oil film thickness and inlet pressure, the three-lobe journal bearing has the highest stability among the three kinds of bearing, which is hard to cause oil film oscillation and instability; under the same conditions of oil film thickness and eccentricity, the bearing capacity of elliptical bearing is better than that of the three-lobe journal bearing, however, the latter one is more helpful to stable operation of turbine rotors and power units.