The invention relates to an undisturbed soil sampler and a sampling method. The undisturbed soil sampler comprises a drill bit, wherein the drill bit is connected with one end of a drill rod, and the other end of the drill rod is connected with a power box for driving the drill rod to rotate; the drill bit comprises a soil container connected with the drill rod, and a tool bit arranged at the end part of the soil container and used for cutting soil; the side wall of the soil container is provided with a soil cutter in an embedding manner, and the edge direction of the soil cutter is perpendicular to the axis of the soil container; and the soil cutter is connected with a mover driving the soil cutter to rotate and enabling the tool bit at the front end of the soil cutter to transversely cut into the soil in the soil container. The drill rod is driven by the power box to rotate, and the drill rod can drive the tool bit to rotate so as to cut the soil; by virtue of the rotation of the drill bit, the soil at the center enters the soil container, the soil after the drilling can be completely taken out by virtue of the soil container, the situation that the drill rod cannot be unplugged is avoided, a hole position is prevented from being changed in the drilling process, and the drilling efficiency and quality can be improved. By adopting the undisturbed soil sampler and the sampling method, an undisturbed soil sample can be obtained in the case of little disturbance.