To meet the requirements of high-speed and high-sensitivity detection of surface defects of transparent optics, and to solve the problems of the low scanning efficiency of the dark field scattering point confocal imaging and the cross-talk of the line confocal imaging, a “point-to-line” confocal collection device for dark field scattering light is designed by partially breaking the object-image conjugacy constraint of the objective. It breaks through the bottleneck of mutual restriction between numerical aperture and field of view, and greatly increases the line field of view from “millimeter” to “hundred millimeter”. A high-speed laser line scanning strategy is designed to illuminate the tested surface with only one laser spot every moment, avoiding the cross-talk of the scattering light of defects. On this basis, a “point-to-line” confocal dark field laser scattering probe with optical sectioning capability is developed. The probe shows the ability of separation of the scattering light from the front and back surfaces of transparent optics. The experiments show that the effective line field of view of the probe reaches 100 mm and the scattering light collection uniformity is 80.7%. For a transparent optical element with a thickness of 2 mm, the signal-to-noise ratio for suppressing back-surface scattered light is up to 14.1 dB. The system has a scanning efficiency of 800 mm²/s at a scan speed of 8 mm/s, a lateral resolution of 20 μm, a signal-to-noise ratio of the scattering signal of 10.9 dB for a fine scratch with a width of 1.16 μm, and a figure of merit of 6.9 cm^-2·s^-1·μm^-1.