At the beginning of mass production，the bubbles in waterborne top coat appeared on the mature production line，which seriously affected the efficiency of production. In this paper，the equipment，process conditions，materials and other aspects were tested andthe reasons were speculated and analyzed. It was found that the number of bubbles in thewaterborne paint could be effectively reduced by reducing the robot spraying flow rate androtating speed of the rotating cup，increasing the flash drying temperature，reducing the baking temperature，and adding 1% H-7 defoamer. According to the results，practical measures had been formulated to effectively solve the occurrence of bubbles，which provided investigationmethods and solutions for future production and other manufacturers to reoccur such relatedquality problems.