The formulations of two waterborne primers and one waterborne matte solidcolor topcoat were designed. The interaction between the different primers and topcoat paintsby wet-on-wet spraying process（3C1B） and the three-coat-two-bake spraying process（3C2B）were studied by contact angle measuring device and depth of field microscope. Thesurface energy of different coatings and the surface/section morphologies of different coatingswere analyzed. The results showed that the motion ability of the coating resins was the mainfactor affecting the interaction between the primers and topcoat paints in the process of wet-on-wet spraying process. Compared with the polyacrylate dispersion，when the polyacrylate emulsion was used as primer resin，because the emulsion particle had intramolecular crosslingking structure，which restricted the movement of segment，leading to a clear interface wasformed between the primer and topcoat paints. This result showed that the molecular segmentalmobility of primer resin was the major factor to affect the interaction between primers andtopcoat paints，which was a key point when designing a primer for 3C1B.