In this paper, we used femtosecond laser with a wavelength of 1040 nm, a pulse duration of 388 fs, and repetition frequency of 100 kHz to etch microgrooves with a large depth-to-width ratio on the surface of quartz glass. Firstly, the laser-induced damage threshold of quart glass was experimentally determined to be 10.61 J/cm ² by virtue of the area calculation method. Secondly, the effects of laser single-pulse energy, scanning speed, and scanning times on the etching depth and width of the microgrooves were investigated with a single-line etching method. Finally, applying spiral etching with assistance of a laser scanning galvanometer, we found that the depth-to-width ratio of the microgrooves could be increased significantly. Experimental results indicate that the laser single-pulse energy plays an important role on the depth-to-width ratio of the microgrooves. Besides, with a laser single-pulse energy of 110 μJ, a scanning speed of 100 mm/s, and a scanning times of 30, we obtain the high-quality microgrooves with a width of 50 μm and a depth-to-width ratio of 5.4 on the surface of quartz glass.