The effects of glass transition temperature(T_g)of emulsion,chemical cross-link,UV cross-link,core-shell technique on the dirt-pick-up resistance of paint film was investigated.Surface energy(polar/disperse portion) was used as an analysis aid to study the change of dirt-pick-up performance of paint film with the speciality of coating emulsion.The results show that for certain type emulsion(styrene-acrylic or acrylic),as T_g increases the disperse portion of surface energy of coating film increases,which shows good agreement to the improving of dirt-pick-up resistant with increasing T_g.For different type of emulsion with similar T_g,the disperse portion of surface energy of silicon-acrylic coated film is higher than styrene-acrylic or acrylic coated one,which agrees well with the better dirt-pick-up resistant performance of silicon-acrylic emulsion compared with styrene-acrylic or acrylic emulsion with similar T_g.