The work aims toimprove the corrosion resistance of the micro-arc oxidation (MAO) coatings by layered double hydroxide (LDH).Firstly, the MAO coatings of Mg alloy were prepared in silicate, phosphate and aluminate-based electrolytes. Then the LDH was grown in situ on surface of MAO coatings. The samples were immersed in an autoclave and mixed with aluminum nitrate and zinc nitrate solution. Scanning electron microscopy, XRD, water contact angle measuring system and electrochemical corrosion tests were used to explore the micromorphology, composition and corrosion resistance of the coatings. The experimental results show that the LDH layer formed in aluminate system is thick and dense, while the amount of hydrotalcite was small and micro-pores and micro-cracks of MAO coatings were not completely closed by LDH in silicate and phosphate system. The results of XRD indicated that LDH had grown in situ on surface of MAO coatings. In silicate system, the contact angles of the composite coatings prepared under 400 V and 430 V conditions were 74.3° and 130.3°, respectively. The composite coating prepared in phosphate and aluminate has a low contact angle, without a hydrophobic. In silicate system, the composite coating prepared at 430 V has an impedance modulus of composite film of 2×107 Ω×cm2, with the corrosion resistance increasing by about 10 times. In situ LDH has a great influence on the corrosion resistance of the coating, and the voltage has no significant influence on the LDH.