Cardboard filter is a new generation technology used in paint overspray separation process of automotive coating industry.The basic separation theory is when air flow with paint overspray pass through labyrinth channels in cardboard filter,paint overspray collide with and be trapped by interior surfaces during several baffling so that paint overspray and air flow are separated.Based on computational fluid dynamics,the paint overspray filtration theory of cardboard filter is simulated by using discrete phase model.The influence to pressure difference and paint overspray filtration efficiency is analyzed on different air speed,overspray mass flowrate and overspray particle size,and simulation data could be reference for paint overspray filtration system planning.The results show that the higher air velocity,the higher pressure difference between cardboard filter inlet&outlet and filtration efficiency will be,the lower overspray particle mass flow rate and higher particle diameter,the higher filtration efficiency will be.