The characteristic height of the magnetic head has down to the nanoscale,and the gas shows obviously rarefied effect characteristics at this micro gaps.The control equation introducing the rarefied effect was established and solved successfully using numerical method based on special treatment scheme.The effect of the surface structure on the gas film rarefied region and flying attitude was analyzed by numerical analysis and experimental tests.The results show that:the gas flow regime divided depending on the inverse Knudsen number is more reasonable than that only from the view of film thickness;negative slider mainly works in the slip flow and transition regions and the area proportion of transition regions is significantly higher than that of the slip regions;the maximum rarefied effect occurs at the side edges where the flying height is thinner and the pressure is lower but not in the minimum flying height on the rear;the variations of the U-shaped slider,both trailing sides slider and the trailing intermediate slider of the magnetic head makes the air flow changes,which directly affects the pressure distribution and rarefied regions of the gas film.