A light guide plate (10) includes a pair of opposite incidence surfaces (101, 103), an emission surface (108) and a bottom surface (109) opposite to the emission surface. A plurality of dots (11) is distributed on the bottom surface, and each dot is shaped as a rectangle or a square. In a pitch of every two adjacent dots, at least one side of one dot has at least one cutout (111), and at least one side of the other dot has at least one corresponding protrusion (119). This ensures that a clearance between adjacent dots is relatively small, thus, the light guide plate can provide emission of light beams with good uniformity. Furthermore, clearances between adjacent columns of dots are discontinuous, and this can avoid bright lines. Thus, the light guide plate can provide improved display quality. Therefore, the light guide plate can be advantageously applied in back light systems of liquid crystal display devices.