In order to improve the stability of polyaniline（PANI）coating during long-term service in acidic environment，PANI was first modified by polyethylpyrrolidone（PVP） through one-step electropolymerization to obtain the PANI-PVP primer coating，and subsequently a macromolecular proton acid（phytic acid，PA）doped polypyrrole（PPY）top coating was electrodeposited to construct the PANI-PVP/PPY composite coating system. The differences in composition，structure，and corrosion resistance between the PANI-PVP/PPY and PANI-PVP coatings were investigated through FT-IR，SEM，and electrochemical tests. The results showed that the modification by PVP significantly improved the compactness，reduced pore defects and the corrosion current density of PANI，meanwhile，the introduction of PPY coating improved the electrical conductivity of the composite coating to provide a satisfactory anodic protection effect. Moreover，the PANI-PVP/PPY composite coating couldstill provide efficient corrosion protection for stainless steel after 360 h service，presenting stable corrosion protection performance.