Abstract: The gas flows and heat transfer in microscale air slider bearings were numerically simulated using a developed DSMC method. The effects of bearing geometry, slider velocity, wall temperature, and surrounding pressure on the pressure distribution within the bearing and the carrying capacity were investigated. The results showed that the bearing geometry and the slider velocity had great effects on the bearing performance. For a bearing with a given length, the pressure peak and the carrying capacity increased with increasing slider velocity and decreasing size of the slider outlet. At fixed bearing geometry and slider velocity, the wall temperature and the surrounding pressure also had important effects on the bearing performance. Higher wall temperature corresponded to a higher carrying capacity of the bearing. The bearing had different performance at different surrounding pressure.