The effect of austenitizing process on the thickness of Al2O3 scale and microstructure evolution of Al-10wt.%Si coating were investigated. The increase of Al2O3 scale thickness and microstructural evolution of hot-dipped Al-10wt.%Si coating on 22MnB5 steel during austenitizing process were studied by scanning electron microscopy(SEM), glow discharge optical emission spectrometer(GD-OES) and X-ray diffractometer (XRD). When the sample was heated to 900 ℃ at the rate of 15 ℃/s, the Al2O3 scale was the thinnest. When the sample was heated to 900 ℃ before holding for 5 min, the Al2O3 scale of coating have cracked in varying degrees. There were some holes on the surface of coating, and the thickness of Al2O3 scale increased obviously. The depth of oxygen infiltrated into Al-10wt.%Si coating and the thickness of Al2O3 scale increased gradually with the prolongation of holding time. The effect of austenitizing holding time on the Al2O3 scale thickness was greater than that of austenitizing heating rate. Reducing austenitizing holding time was beneficial to preserving a complete Al2O3 scale and protecting the steel substrate. The microstructural evolution of Al-10wt.%Si coating was as follows: First, Al2Fe3Si3(τ1) and Fe2Al5 phases formed. Next, Fe2Al5 grew, FeAl2 phase formed, and FeAl2+Fe2Al5 phase grew, FeAl precipitated. Then, FeAl phase grew, some holes appeared on the Al2O3 scale. Finally, the Al2O3 scale cracked, the number of holes on the surface of coating increased. The final microstructure of coating was FeAl2+Fe2Al5+FeAl.