The effect of KI on the surface micrograph of electroless Ni-P coating for 2024 aluminum alloy was observed using scanning electron microscopy (SEM), and corrosion resistance of Ni-P coating in 3.5%NaCl solution was investigated by immersion, potendynamic polarization curves and electrochemical impedance spectroscopy(EIS). The experimental results show that KI reduces the amount of defect such pole in Ni-P coating, and the crystal grain becomes finer. The surface morphology of Ni-P coating gets more homogenous and smoother. Moreover, the phosphorus content of Ni-P coating is increased by KI. Both factors contribute to a better corrosion resistance for Ni-P coating in 3.5% NaCl solution.