Oxide ceramic layer was obtained on Ti-6Al-4V alloy in NaAlO_2, Na_3PO_4 mixed solution by micro-arc oxidation (MAO) technique. The structure and composition of MAO coatings were analyzed by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results show: the surface and interface have the porous structure, but the difference between the diameter of pores in surface is quite large, the difference in interface is quite small, and there are some long hill paralleled to each other in interface. There is no obvious boundary between the loose layer and dense layer. The interface between the substrate and MAO coatings has a z-zig structure. The surface and interface are composed of Ti, Al, V, P elements, and Al element is inclined to enrich in surface, but P element enriched in interface according to EDS results. TiO_2, Al_2O_3, TiAl_2O_5 phases are identified in surface and interface, and the P element exists in PO_4~(3-) radical according to XPS analysis. V_2O_5 phase can be found in the interface and V element does not exist in the surface according to XPS analysis.