The poly(methyl methacrylate) (PMMA)/poly(methyl methacrylate)-poly(methyl acrylate acid) copolymer (PMMA-PMAA) composite polymer latex were synthesized by the method of soapless seeded emulsion polymerization. The morphology of the composite polymer latex was core-shell structure. The core was PMMA and shell was PMMA-PMAA copolymer. Because the PMMA-PMAA copolymer was shell, the carboxylic acid functional groups (COOH) of MAA distributed on the surface of composite polymer latex. The concentration of carboxylic acid groups distributed on the surface of composite polymer latex could be controlled by the amount of MAA. Antigens (Bovine Serum Albumin (BSA) or Anti-human IgG) were chemically bound onto the surface of PMMA/PMMA-PMAA core-shed composite latex by the method of either pre-activation or pre-adsorption to form the protein-coated latex (immunolatices). The more the carboxylic acid groups on the latex, the more the antigens were bound onto the surface of PMMA/PMMA-PMAA core-shell composite latex. The immunolatices had the higher stability than the parent composite latex due to the effect of steric hindrance of the antigens. Moreover, the sensitivity of the immunological agglutination of immunolatices was significantly influenced by the amount of covalently bound antigens and temperature.