Milling of Al2O3 ceramic is affected by various factors. Combination of laser milling parameters was optimized based on orthogonal experiment in this study. The affect degree of the parameters on the milling depth was obtained by range analysis ,based on which process parameters were optimized and laser milling experiment was taken on circular cavity using optimized parameters. The results indicated that the sequence of the factors affecting on the milling depth was laser power,scanning speed, overlap amount,defocused quantity successively. By using optimized parameters,milling depth of 0.4mm was obtained for single layer experiment,and milling result was satisfactory. The roughness was increased because the molten on the specimen surface failed to be removed,thus the pressure of the assist huff gas should be increased to improve the surface quality.