The most suitable defoamer for water based acrylic adhesive was chosen by analyzing the property of organic and molecular defoamer in the foaming solution and waterborne acrylic emulsion. Adding process and test methods of the antifoaming performance and defoaming mechanism were investigated. The results show that the compatibility of the defoamer is inversely proportional to the defoaming ability. Dynamic adsorption of 02% defoamer in foaming solution is diffusion controlled in short time. Molecular level defoamers are suitable for “bridging stretching” mechanism while organic defoamers are suitable for both “bridging stretching” and “bridging dewetting” mechanisms. The addition of defoamer has no notable effect on the viscosity, particle size and storage stability of waterborne acrylic adhesive emulsion.