The work aims to improve the wear resistance of D16T aluminum alloy. A micro-arc oxidation ceramic coating was produced on the surface of D16T aluminum alloy with the micro-arc oxidation technique by adding 2 g/L nano-TiO2 additive to the mixed electrolyte system of silicate and phosphate. The effect and mechanism of nano-TiO2 additive on the structure and wear resistance of the coatings formed on D16T aluminum alloy were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy spectrum analyzer (EDS), microhardness tester, thickness tester and friction and wear tester. The surface of micro-arc oxide coating became more smooth and denser and had fewer micropores and cracks due to nano-TiO2, thus greatly improving the coating structure. Compared to the micro-arc oxidation coating prepared in the electrolyte without nano-TiO2, the new phase TiO2 was formed in the micro-arc oxidation coating prepared in the electrolyte containing nano-TiO2, and more α-Al2O3 and γ-Al2O3 phases were formed. Therefore, the thickness of the coating with nano-TiO2 was obviously increased and up to 31.2 μm, and the microhardness was also significantly improved to 510HV. The friction coefficient of D16T micro-arc oxidation coating was reduced and the average friction coefficient was 0.45 which was smaller than 0.75 of the coating without nano-TiO2. The nano-TiO2 added to the electrolyte has entered the formed oxidation coating during micro-arc oxidation reaction and filled the micropores and cracks in the coating. Therefore, the coating structure is improved and the coating thickness is increased, which significantly improves the microhardness and wear resistance of micro-arc oxidation coating.