In order to study the hydrothermal reaction mechanism of layered double hydroxides (LDH) and the effect of hydrothermal treatment temperature on the microstructure and corrosion resistance of MAO/LDH composite coating, hydrothermal treatment temperature was changed, while hydrothermal time was maintained at 18 hours, and LDH were prepared on the surface of the MAO ceramic layer of LA103Z Mg-Li alloy. Then immersion experiment and hydrogen evolution experiment were carried out in a 3.5% NaCl solution. The composite coating was characterized by XRD, SEM, and EDS. After the hydrothermal treatment, fine texture structures can be formed on the surface of MAO coating at different hydrothermal temperatures. Through XRD analysis, the characteristic peaks of LDH were found. The surface of LDH coating prepared at 80 ℃, 90 ℃ and 100 ℃ was uniform and cross-section structure was dense. The size of texture structure of LDH coating prepared at 120 ℃ was coarser, and the surface was more densely, but cross section was fluffy. In the hydrogen evolution experiment, the slopes of hydrogen evolution curves of the composite coating at different hydrothermal temperatures showed 80 ℃≈90 ℃<100 ℃<120 ℃< LA103Z substrate. Among them, the amount of hydrogen evolution of the LDH coating prepared at 80 ℃, 90 ℃ and 100 ℃ for 8 days was less than 50 mL, which was much lower than 150 mL of 120 ℃. The results show that during the hydrothermal treatment, Mg(OH)2 is first formed on the surface of MAO ceramic layer, then Al3+ in the solution replaces the position of Mg2+ in Mg(OH)2 to form LDH, and finally grows into LDH coating. Within a certain temperature range, the corrosion resistance of Mg-Al LDH/MAO composite coating is gradually enhanced with the decrease of preparation temperature, which is closely related to its microstructure.