Abstract: Investigates the sump shape, contact level between melt and mould, forming position of initial solidified shell and depth of sump of 6063 Al-alloy during the semi-continuous casting with air film used. The results showed that in comparison to hot top casting the application of air film to the casting process can lower the useful heat sink intensity of the mould and heighten the contact level between melt and mould, at the same time the forming position of initial solidified shell lowered and relatively flat sump shape. The lowered position of initial shell results in reducing the backheating of ingot and eliminating the segregation and cold shuts, the surface quality was greatly improved.