Abstract: On the basis of an analysis on the feeding pattern of the coating material, its behavior in the laser beam, distribution of laser energy and the attenuation of laser beam caused by particle's cloud during the process of laser coating, the methods to calculate the interaction efficiency of laser and particles speed are presented. Then an analytical model of the molten oppl depth was establised,relating to the parameters of the processes, As the molten pool depth was calculated by the oretical method and compared with measurments of metallography, it is found that the theoretical results is higher than the experimental results, but they coincide well with each other quantitatively and are consistent in reflecting the objective realty of the process. For given laser parameters, the molten pool depth becones smaller with the increase of powder feeding rate and scanning speed. This model is helpful to optimize process parameters, understand the major relationship between the process parameters and the results, and design on-time control system.