The work aims to study effects of temperature field distribution during micro-arc oxidation process on film formation process and morphology. With a discharge channel of 7075 aluminum alloy as object of study, a mathematical model and a physical model were established for micro-arc oxidation heat transfer process based on the multi-physics simulation software COMSOL Mutiphysics. The temperature field distribution of the micro-arc oxidation film forming process was solved in finite element method. Some specific reference lines and reference points were selected to plot temperature-time curve; key time points including 0, 100, 500, 1000 μs were selected to plot temperature-longitudinal depth curve, temperature distribution chart and temperature gradient distribution chart. Their effects on morphology of the ceramic layer were investigated as well. In 0~100 μs, temperature of the discharge channel region decreased at the fastest speed; in 100~500 μs, the temperature descending rate decreased gradually; in 500~1000 μs, the temperature drop rate was the smallest and tended to be constant; compared with that in the discharge channel central area, temperature drop was faster and the temperature gradient was larger near alumina film-aluminum alloy interface; at 0, 100, 500, 1000 μs , longitudinal depth of the maximum temperature position was 93, 20, 26, 38 μm, tending to decrease first and increased later. Cooling effect of the electrolyte on the micro-arc oxidation process is mainly present within 100 μs after the discharge channel takes shape; in addition to the electrolyte, the alumina-aluminum alloy interface has also played a certain role during this process, and unbalanced cooling rate in each area of the discharge channel is the main cause of formation of the crater-like holes on the oxide film surface.