Under the reservoir conditions of Wen 120 block in Huabei oilfield with 87℃ and 28291 mg/L salinity, the effect of permeability ratio on oil displacement efficiency of air foam flooding was researched with four groups of physical models which were made of different mesh number of quartz sand, whose permeability ratio was 2.8, 6.8, 8.9 and 10.7 respectively. The results showed that the enhanced oil recovery rate of high permeable tube, low permeable tube and double tube increased first and then decreased with increasing permeability ratio. When the permeability ratio increased from 2.8 to 8.9, the enhanced oil recovery rate of high permeable tube increased from 15.13% to 18.56%, that of low permeable tube increased from 19.45% to 29.81%, and that of double tube increased from 17.24% to 23.43%. The foam system enhanced the ability of profile control and water plugging in high and low permeability layer, and the effect of oil displacement became better. When the permeability ratio reached 10.7, the enhanced oil recovery rate of high permeable tube, low permeable tube and double tube was 13.55%, 9.00% and 11.74% respectively. The ability of profile control and water plugging of foam system reduced in high and low permeability layer, and the effect of oil displacement became worse.