The phosphorylated styrene-acrylic rust preventive emulsion (PM-2-SP) with core-shell structure was synthesized by semi-continuous seeded emulsion polymerization using methacrylic acid (MAA), hydroxypropyl methacrylate (HPMA) as a crosslinking monomer, styrene (St) and methyl methacrylate (MMA) as hard monomer, butyl acrylate (BA) as Soft monomer, 2-hydroxyethyl methacrylate phosphate (PM-2) as a functional monomer and dodecanethiol as a segment regulator. The effects of the amount of PM-2 on the stability of PM-2-SP emulsion, the water resistance of the PM-2-SP film and the anti-rust properties of the film were studied. Also, the size and morphology of the PM-2-SP emulsion particles were characterized by DLS and TEM. The surface of the film was observed by atomic force microscopy (AFM). The corrosion resistance of the paint film was tested using a salt spray tester. Consequently, the results show that the emulsification of the system and anti-rust performance of the paint film were optimal when the content of PM-2 is 4wt%. The particle size of PM-2-SP emulsion with core-shell structure was 135.7nm and the PDI was as low as 0.150. The film had the smooth and compact surface as well as excellent resistance to water. In addition,The corrosion potential and corrosion current of the film was -0.391V and 1.95E-7(A?cm2), respectively. What's more, compared with pure styrene-acrylic, the rising rate of corrosion potential and reduction rate of corrosion current of the film was 74.16% and 94.76%, respectively. The salt spray resistance time of the film had extended to 144h.