Abstract: To obtain better result of laser etching, micro-machining of alumina ceramics with ultraviolet(UV) laser (355nm) was conducted in air and water respectively. The impact of laser parameters, such as laser fluence, scan speed, and laser frequency on the etching depth was investigated. The mechanism of laser etching and the physical process of water-assisted etching were studied. Etching morphology in air and water with UV laser and etching depth with different laser parameters were obtained. The results show that water-assisted laser etching can improve the etching efficiency and etching surface quality. The etching depth has close relationship with laser fluence, scan speed, laser frequency and water depth. The water cooling effect and vacuum occurring during water-assisted etching could prevent the secondary adhesion to the eclipse material effectively and the formation of metamorphic layer.