To understand the material removal mechanism better in laser cutting, the shape and characteristic parameter distribution of removal melt particles are obtained through image processing with imagine-pro plus (IPP) software. Laser cutting of 1000 series aluminum alloy sheets with thickness of 0.85 mm, is carried out based on the vapour-melt ratio controlled. The removal melt particles are classified three kinds of shape through the metric rule, including the rounded particle, the quasi-rounded particle and the tadpole-shape particle. The results show the percentage of rounded particles increases in removal melt particles with vapour-melt ratio increasing, but the percentage of quasi-rounded and tadpole-shape decreases, and the average size of particles reduces with vapour-melt ratio increasing. Also the cutting quality improves with the increase of vapour-melt ratio in test. A removal model is established, which indicates that the cutting quality has a significant relationship with removal melt. Finally the high quality cutting and the slot array antenna sheet are obtained.