Due to the microfabrication limitations,the bow defect of the journal bearing defined by the clearance between the rotor and static structure is inevitable.The bow defect leads to the variation of the clearance along the bearing length.The bowed gas film thickness equation was combined with the molecular gasfilm lubrication model so that both the gas rarefaction effects and the bow effect were introduced simultaneously.The NewtonRaphson method was adopted to solve the nonlinear equations.The normal mode method was utilized to derive the mathematic model for assessing the dynamic properties and the stability charts of the micro gas bearing system.The results indicate that the bow effect lessens the pressure distribution of the gas film,weakens the load capacity and stiffness coefficients of the system,and increases the required stable minimum eccentricity.The curves of critical mass value move upward compared with the ideal bearing with the same minimum clearance.Meanwhile,bearing systems with bow defect is more liable to become unstable for high bearing number and eccentricity than ideal bearings,and more influence will happen when the degree of bow defect becomes larger.