Abstract: Parameters of coating machine make a great impact on the thickness of the protective coating in the sawing process of the 12 inch wafer. To improve the productivity and process quality, the uniform design was used to study thickness of the film relating to the factor of scale of micrometer valve, flux pressure, and atomizing pressure. A significant mathematical model was obtained by using SPSS based on the non-linear regression analysis of experimental data, and it reveals the interactive relationship between the factors and provides a basis for machine adjustment. This model has been successfully applied to an chipset assembly/test (A/T) factory and the adjustment time has been significant reduced.