The invention discloses waterborne 
coil coating polyester rear face paint and a preparation method thereof. The rear face paint comprises, by weight, 30-40 parts of 
polyester resin, 30-35 parts of 
pigment filler, 7-10 parts of amino resin, 0-0.5 part of dispersant, 0.1-0.5 part of an anti-
settling agent, 0.5-1.2 parts of an antifoaming agent, 0.5-3 parts of adhesion 
promoter, 0.1-0.5 part of an acid catalyst, 0.1-0.5 part of a 
wax auxiliary agent, 0.1-0.3 part of a flatting agent, 0.1-2 parts of 
extinction powder, 4-6 parts of butyl cellosolve, 2-4 part of isopropanol and 35-40 parts of water. The invention further discloses the preparation method of the rear face paint. According to the waterborne 
coil coating polyester rear face paint and the preparation method thereof, water serves as a dispersion medium, so that the rear face paint has the advantages of being 
environmentally friendly, low in cost, excellent in scratch resistance, 
corrosion resistance and 
solvent resistance, not sticky, good in foaming performance and the like, and the rear face paint is equivalent to 
solvent type polyester rear face paint in performance; waterborne 
rust resistance is achieved, and 
corrosion resistance is more excellent.