Abstract: Cationic polystyrene-acrylate emulsion was modified by perfluoralkylacrylate with two-stage emulsifier-free polymerization，in which 2-(perfluoroalkyl)ethyl acrylate was used as the fluoro containing monomer，methacryloxyethyltrimethyl ammonium chloride（DMC）and acrylamide（AM）were used as the cationic and hydrophilic monomers，respectively. Structure and thermal stability of the copolymer were characterized by FTIR and thermogravimetic analysis（TGA），respectively. Effect of the fluoro-monomer content and temperature on the surface free energy of the copolymer latex films was analyzed. Results showed that when FEA content used in the copolymerization increased from 1.2% to 5%，the surface free energy of the copolymer films decreased drastically from 23.54 mJ/m2 to 15.27 mJ/m2. With a further increase in FEA content，the surface free energy reduced slowly. When FEA content increased to 9.8%，the surface free energy decreased to 14.83 mJ/m2. Through annelaing treatment of copolymer latex films with the temperature increase from 25 ℃ to 120 ℃，the surface free energy decreased from 15.27 mJ/m2 to 14.06 mJ/m2.