Sodium fluoroaluminate conversion coating on the surface of 6063 aluminum alloy was modified. The optimal operation parameters were as follows: NaF 7 . 5 g / L, Na₂SiO₃5 g / L, ( NaPO₃)₆3 g / L, NH₄VO₃5 g / L, pH 3 . 0 ~ 4 . 0 , ordinary temperature, 20 minutes. After conversion treatment by the process, the polarization curve measurement of the Al alloy showed that corrosion potential increased by about 70 mV and corrosion current density decreased by about 90 % , the corrosion resistance of the Al alloy was improved obviously, the neutral salty test time of Al specimen reached up to 264 hours.