This paper aims to reduce the risk of magnesium alloys fire under high temperature and verify the ignition resistance of the micro-arc oxidation (MAO) coatings. The MAO ceramic coatings on AZ91D magnesium alloy were fabricated by adding potassium fluorozirconate (K2ZrF6) into alkaline silicate electrolyte, and the influence of K2ZrF6 on ignition resistance of the coatings were studied. The microstructure of the coatings before ignition were observed by Scanning Electron Microscope (SEM), and X-ray Diffraction Spectrometer (XRD) was used for the phase identification. Ignition resistance of MAO coatings formed on AZ91D magnesium alloy in different content K2ZrF6 were investigated by the ignition resistance torch test. The coatings fabricated in K2ZrF6-containing electrolyte are mainly composed of MgO, Mg2SiO4, MgF2 and ZrO2. The number of large size defects in the MAO coatings is reduced, the density and thickness increase gradually and the surface roughness increases firstly and then decreases with the increasing of K2ZrF6 content. The MAO coatings formed in 0~10 g/L K2ZrF6 electrolyte have the poor densification and tend to appear a large number of ablative holes and longitudinal propagation cracks under high temperature flame. The MAO coatings prepared in 15 g/L and 20 g/L K2ZrF6 electrolyte have the denser inner structure, and do not lose their protection until the matrix is completely melted and deformed, forming transverse propagation cracks. Under the K2ZrF6 concentration of 15 g/L, the coating has the longest ignition time and the best ignition resistance. The effect of K2ZrF6 concentration on the ignition resistance of the MAO coatings is mainly through increasing the density of the coatings to enhance the ignition resistance. The dense structure of the inner layer can reduce the ablative holes and delay the propagation of crack under the high temperature flame, thus preventing the outward diffusion of molten liquid magnesium and magnesium vapor, slowing down the oxidation reaction and improving the ignition resistance of the coating.