Abstract: In order to investigate the validity of gas lubrication theory in head/disk interface when ultra-high aeral density was achieved by using patterned media technology, a three dimensional slider bearing model with bumps was devised and simulated using both Direct Simulation Monte Carlo (DSMC) and Molecule Gas-Film lubrication (MGL) Method. The effects of relative sliding velocity, bearing clearance, bump height and angle of incidence on pressure distribution of gas slider bearing were considered. Results indicated that the difference between results of MGL and DSMC method was slight for this three dimensional slider bearing with bumps. In situation of bump contact and bearing clearance approaching zero, gas slider bearings still had certain bearing capability, and the trends of pressure distribution varying with bump height were different from conventional non-contact slider bearings.