Spray coating is one of the most important applications in the industry. The deposition properties of droplet onto surface can be determined by Weber number and K number. While the relationship between the Weber number, the K number and the operating conditions is not understood. In this paper, a comprehensive numerical model based on the Navier-Stokes equation and the particle tracking method was used to simulate numerically the effervescent atomization spray with an impinging surface, and an analytical model was used to predict the droplet velocity. After performing extensive computations at different operating conditions, the formulae of droplet diameter and droplet velocity were obtained with curve fitting technique. The results Calculated from the formulae agree with the experimental data. Finally the new formulae relating the Weber number and the K number to the operating parameters were deduced out. The new formulae can be conveniently used to judge the deposition property of droplet onto surface. (C) 2008 Elsevier B.V. All rights reserved.