Abstract: In order to achieve the optimum parameters of laser-induced backside wet etching for the fabrication of microchannel of silica glass, experiments were made by changing the laser power, etching velocity and magnification times of microscope objective. The processing samples were observed and measured by digital microscope. And then, the topography of microchannels was analyzed. The results show that, under the experimental conditions of laser power of 50mW, etching velocity of 0.010mm/s and 20^× microscope objective lens, microchannels of silica glass were fabricated with the depth of 1466μm and the ratio of depth to width of 32. This research has certain application value for micronano fabrication technology of 3-D structure.