In this paper, poly(styrene-acrylate) latex with phosphate functional group (SA-PO) was prepared using mini-emulsion polymerization. Polyaniline (PANI) bonded SA (PANI-SA) composite was then prepared by in situ chemical oxidation polymerization of aniline. FT-IR and UV-Vis spectra confirm the formation of the PANI-SA composite. Small spherical particles of 10-20 nm in diameter on the surface of SA latexes are observed by SEM. DSC and TGA results indicate that there are chemical bonds formed between PANI and SA, and PANI in the PANI-SA composite can increase the glass transition temperature (T (g)) and thermal decomposition temperature (T (d)) of SA latex film effectively. Mechanical property testing indicates that PANI in PANI-SA composite can increase the mechanical properties of SA latex film. EIS measurements show that PANI in SA-PANI can significantly improve the corrosion resistance performance of waterborne SA coating. Compared with PANI/polymer composite system, PANI-SA has two advantages: avoidance of the aggregation problem of nanoscale PANI in polymer matrix and improvement of the interface adhesion between PANI and polymer matrix.