Abstract: A line velocity interferometer for any reflector has been implemented at the Shenguang-Ⅱ laser facility. This instrument is the primary diagnostic for a variety of experiments involving laser-driven shock-wave propagation, materials characterization experiments and shock timing experiments. It measures velocities of interfaces, free surfaces and shock fronts traveling through transparent media. It can measure shock breakout time at temporal resolutions as low as 20 ps, and spatial resolution 10 μm. Experiments were carried out on the Shenguang-Ⅱ laser facility and high quality interference images were obtained.