A numerical model has been suggested to predict and analyze the shape of a growing billet produced by spray casting process using the scanning gas atomizer. It is important to understand the mechanism of billet growth because a billet with a desired final shape can be obtained by optimum combination of several process parameters. The shape of a growing billet has been determined by the flow rate of alloy melt, spray mass distribution, rotation and withdrawal speed of the substrate, and scanning motion of the gas atomizer. Scanning motion has been controlled by the profile of cam which determines scanning angle and scanning speed of the gas atomizer. The effects of the most dominant process parameters, such a s withdrawal speed of the substrate and the cam profile, on the shape of the growing billet have been discussed. This numerical model can also serve as a basis for heat transfer analysis of the growing billet.