A phytic acid conversion coating was developed on AZ31 magnesium alloy by dipping the magnesium alloy into the phytic acid solution. The effects of heat treatment in the temperature range of 150 degrees C-400 degrees C on the chemical composition of the coatings and the crack healing were investigated, and the corrosion resistance of the coatings in simulated body fluid was studied by electrochemical measurements. The results showed that with the increase of the heat treatment temperature, the cracks on the surface of the conversion coating gradually healed up, that subsequently improved the corrosion resistance of these coated magnesium alloy. During the heat treatment process, the conversion coating composed of amorphous magnesium phytate was transformed to crystalline Mg2P2O7. Meanwhile, the macromolecular complex changed into small organic structure, and accompanied the increase of the volume, leading to the surface crack self-healing. The coating heat-treated at 400 degrees C exhibited superior surface integrity and corrosion resistance due to the great crystallization of Mg2P2O7 and crack healing. Published by Elsevier B.V.