The environmental friendly water-based styrene-acryl ate micro-emulsion coatings polymerization is prepared by the process of micro-emulsion seeded polymerization of styrene and the polymerization method, and temperature, soft / hard monomer ratio and the amount and ratio of emulsifier on the emulsion and coating properties are discussed. The results indicate that the use of emulsifiers of SDS/OP-10 and the way of pressed emulsion polymerization can get the micro-emulsion with the solid content of 47.2 percent. When compared with other methods, the emulsifier can reduced by nearly half. Integrate considerations of micro-emulsion performance, soft / hard monomer with more appropriate ratio mMMA:mSt:mBA＝35:20:26; emulsion of the two-stage synthesis emulsifier content is: mA-102:mDNS-86=2.5:1, so it proves that micro-emulsion synthesis have a good stability and the coating showed good properties of water resistance.