In this paper, fiber laser is used to laser quench the surface layer of rail material U75V. The surface flatness of the rail specimen after laser quenching is no different from that before quenching. The quenching depth at the center of the laser heat source is the deepest, about 1 mm. The center position is a very fine acicular martensite structure, at the overlapping position. The grains in the laser secondary quenching zone will be refined again. The latter pass has an obvious thermal effect on the former pass, resulting in a coarse retained austenite structure. The U75V laser quenching hardness of the rail is as high as about 850 HV, the effect of hardness improvement is obvious.