In this paper, organosilicone modified styrene-acrylic (OSA) latexes for waterproof coating were synthesized through core-shell emulsion polymerization. The influence of emulsifier type and dosage on the size, size distribution and morphology of the latex was systematically investigated. The water absorbance and thermal decomposition behavior and the mechanical properties of the waterproof coating depending on the organosilicone introduced on the latex shell were also studied. Transmission electron microscopy and dynamic light scattering results indicated that the particles had a regular spherical morphology with different diameters and distributions. Thermal gravimetric analysis results revealed that the thermal stability of the latex films was improved with the introduction of organosilicone. The waterproof property of the OSA latex film was obviously increased as compared to that of the styrene-acrylic latex film. The tensile strength and fracture elongation of the elastic waterproof building coating made of the OSA latex and cement powder were significantly greater than that made of the styrene-acrylic latex and cement powder.