On the basis of the preferred emulsion preparation process, the effect of organosilicon monomer dosage on the stability of polymer emulsion in the cement system was investigated through the stability of calcium ion, sieve residue rate and Zeta potential. Moreover, the mechanism of the organosilicon monomer’s influence on the stability of the emulsion was investigated in combination with rheological performance test. The incorporation at a concentration of 2% organosilicon is identified as the optimal level, at which significant enhancements in the anticorrosive and anti-permeability properties of polymer-modified cementitious coating are observed. Relative to commercially available emulsions, coating modified with 2% organosilicon manifest a substantial decrease in electrical conductivity to 772C and exhibit a 35% improvement in resistance to chloride ion penetration.