A high corrosion resistant and active protection composite coating designed combining Layered Double Hydroxides (LDH) layer and Micro-arc Oxidation (MAO) to further improve the anti-corrosion of Mg alloy. In this paper, MgCr-LDHs/MAO composite coating prepared through in-situ growing LDH layer including NO_^3- on the surface of MAO coating. The morphology、composition and microstructure of MgCr-LDHs/MAO composite coating were characterized by XRD, XPS, FT-IR, SEM, besides the interaction of LDH and original MAO coating was investigated. The corrosion properties of MgCr-LDHs/MAO coating was tested through immersion in 3.5wt%NaCl solution and electrochemical experiments. The results show that: (1) the LDHs forms a dense sheet like layer on the original MAO coating surface, which can effectively cover the inherent defects of MAO coating, and LDH layer is preferentially formed in the pores of original MAO coating. (2) LDHs don"t damage the original MAO coating during the growth process, besides the adhesion of LDH layer and MAO layer are strong and stable. (3) The composite coating showed the most superior corrosion protection, since MgCr-LDH layer growing on the original MAO coating can hinder the penetration of chloride ions and effectively adsorb a large number of NO_^3? to exchange Cl_^- in corrosion solution.