The work aims to study the effect of film-forming temperature on the microcracks and corrosion resistance of phosphate conversion films on magnesium alloy based on statistics of size and area of microcracks on the surface of conversion films at different film-shaping temperatures and electrochemical test. Morphology of microcracks obtained at different temperatures was observed by scanning electron microscopy (SEM). Width and area of microcracks on the surface of conversion films were measured by Image-pro-plus software, and corrosion resistance of the conversion films was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Statistical results showed that the microcrack width and area of the conversion film prepared at 50 ℃ were the minimum, 2.68 μm and 1067 μm2, respectively; for the conversion film prepared at 30 ℃, the maximum, 3.14 μm and 1391 μm2, respectively; for the conversion film prepared at 70 ℃, 2.74 μm and 1170 μm2, respectively. The electrochemical test indicated that self-corrosion current of the conversion film prepared at 50 ℃ was the minimum, Jcorr=20.3 μA/cm2, and radius of capacitance arc in the electrochemical impedance spectroscopy was the maximum. Microcracks narrow down and decrease with the increase of film-forming temperature. However, the microcracks broaden and increase at higher temperature. At the film-forming temperature of 50 ℃, the micro cracks are the least and narrowest and are provided with the best corrosion resistance.