In order to satisfy the needs of environmental regulation,paint shop has decided to introduce acid epoxy clear coat which has the double advantages of high solids and low VOC,but a typical pinhole problem appears on three particular colors supplied by same coating company when new clear coat is used.So the morphological characters and the forming mechanism of pinhole were researched firstly,then two primary factors were found,one of which was pearl powders with big size,and the other one was curing speed of acid epoxy clear coat,the former was chose as improvement direction by comparison.To address this issue,four effective measures were systematically analyzed,such as optimization selection of pearl powders,enhancing pre-dispersion effect,adjusting the adding of disperser and solvent,and the use control of pearl powders for color matching.Finally,the typical pinhole problem was eliminated completely through above-mentioned comprehensive measures.