Objective To improve the comprehensive properties of the Ce-Mn conversion coating deposited on 6063 aluminum alloy. Methods The Ce-Mn conversion coating was firstly prepared in the solution mainly containing cerium nitrate and potassium permanganate. After that, the Ce-Mn coating was post-treated in the molybdate solution, the treatment processes were optimized, a novel Ce-Mn/ Mo composite conversion coating was formed and its microstructure and properties were characterized. Results The optimal film formation process parameters were as following: Na2MoO4 18 g/ L, sodium dodecyl benzene sulfonate(SDBS)1. 5 g/ L, conversion time 18 min, deposition temperature 45 ℃. After post-treatment, the color of the Ce-Mn coating changed from golden yellow to brownish-black. The test result showed that the Ce-Mn/ Mo composite coating was uniform and dense tissue. This coating was mainly composed of Ce, Mn, Mo, O and Al elements, and the thickness of Ce-Mn/ Mo composite conversion coating was significantly increased to about 7 μm. The corrosion current density was reduced by about 85% . Conclusion Compared with the CeMn coating, the Ce-Mn / Mo composite coating exhibited excellent corrosion resistance, weatherability and wear resistance.