Abstract: The behavior of pure squeeze film lubrication of journal bearings with micropolar fluids is studied. Modified Reynolds equation based on the theory of micropolar fluids is solved together with the nonlinear motion equation of the journal center. The size of material characteristic length and the coupling number are used as the symbolized parameters of the micropolar fluids.Comprehensive comparisons are made between the Newtonian fluids and the micropolar fluids for the effects on the dynamic behavior of the journal center and the lubricating performance. It is shown that the micropolar lubricants produce an obvious decrease in displacement, velocity and acceleration of the journal center and then the squeeze film bearings operate more stably. Meanwhile the minimum oil film thickness is increased but the maximum pressure and side leakage flow are decreased, which indicates that the load capacity of the squeeze film bearings lubricated by the micropolar fluids is enhanced.