Objective To improve the thickness uniformity of Zn-Cr coatings and to accurately control the machine element, the technological parameters of pretreatment and Zn-Cr coating process were studied. Methods The technological parameters of pretreatment and Zn-Cr coating process were optimized by using the uniform design method. The quality of Zn-Cr coatings could be improved through the control of shot blasting and coating parameters. Results Through the optimization experiment and the calculation using the uniform design software, we achieved an isogram of the coating at different viscosity and spin-dry speed. Based on the isogram, we improved the plating parameters. The surface roughness Ra reached 1. 6 μm, and the thickness accuracy of coatings reached 依1. 5 μm. Conclusion By choosing the suitable coating process according to the isogram, we could efficiently control the adhesive amount of the Zn-Cr coatings and then control the quality of the Zn-Cr coatings.