Abstract: In view of problems of low controllability and poor coating consistency of traditional three-proofing lacquer process affected by factors of technology and environment, an improved three-proofing lacquer coating process for mine-used PCB assembly was proposed. Selection of coating way and material of the three-proofing lacquer was described, method and content of the three-proofing lacquer coating process for mine-used PCB assembly were researched. The experiment result shows that the selection of two-component polyurethane paint and selective spraying method has good consistency of coating, and improves production efficiency.