α-Al2O3 membrane coating（top layer）was formed by dip-coating and the effects of microstructure of supports and technological controllers of film coating，which included dipping time and the flow rates of the suspension into/out the supports，on the membrane thickness were investigated based on experiments.The water flux of supports was used to correlate the support microstructure and its effect on the membrane thickness was studies.The results showed that the membrane thickness increased proportionally with the 1/2 root of dipping time，with 2/3 root of flow rate and increased linearly with the water flux of supports，respectively.In addition，experimental results also showed that the membrane thickness decreased with the increase of dipping time when the dipping time was longer than the saturation time of supports.When the flow rate of the suspension was higher than a certain value，the membrane thickness would no change with the increase of flow rate.