To improve the quality of laser cutting in aluminum alloy sheet, the collected melt is observed and measured. Laser cutting of 1000 series aluminum alloy sheets, with 0.85mm thickness, is carried out on a NdYAG pulsed laser machine under the different vapor-melt ratios of 0.1898, 0.2798, 0.3708 and 0.6519. In experiments the shape and size of collected removal are analyzed by a 3-D microscope. The melt is found to be tadpole-shape particles and spherical particles ranging from 71~123 μm in average diameter. The results show the collected particles are formed spherical at the high vapor-melt ratio and small in average diameter with good cutting quality. In contrast, at the low vapor-melt ratio the form is mainly tadpole-shape and the existence of big spherical particles of which with poor cutting quality. Finally, under the condition of gas pressure of 0.6 MPa and high vapor-melt ratio of 0.6519, the researches achieve higher quality cut. The results help researchers to understand the characteristics of laser cutting in aluminum alloy and improve the laser cutting quality of aluminum alloy sheet effectively.