The work aims to synthesize a cationic fluorinated poly-styrene-acrylic latex, which can be used in cotton fabric finishing. With 2,2‘-azobis(2-methylpropionamidine)dihydrochloride as initiator, cationic fluorinated poly-styrene-acrylic latex was synthesized from perfluoroalkylethyl acrylate, butyl acrylate, methyl methacrylate, styrene and n-hydroxymethyl acrylamide by semi-continuous seed emulsion polymerization . The final copolymerization emulsion was characterized with FT-IR, GPC, DSC and LPSA. Hydrophobicity of the latex film varied slightly with core-shell ratio since organo-fluorine chain segment could automatically migrate to the surface. However, its glass transition temperature rose slightly with the increase of hard monomer content. In addition, as initiator dosage increased, monomer conversion rate and weight-average molecular weight increased, and coagulation rate decreased. The FT-IR test showed that fluorocarbon group and other functional groups were successfully incorporated into copolymers. Furthermore, average diameter of narrowly distributed emulsion measured by laser particle analyzer was 0.196 ?m. The finished cotton fabric had a smooth and flat surface, and was tested to show 95 points in water-proofing and grade 6 in oil-repellency. Reaction process of cationic fluorinated poly-styrene-acrylic latex prepared by core-shell emulsion polymerization is stable. After being processed with it, the cotton fabric surface exhibits excellent waterproof and oil-repellent properties.