A light guide plate, comprising a light guide plate body having an upper surface as a light-exiting surface, characterized in that, the light guide plate body is of a circular or near-circular shape; the light guide plate body is provided at a side portion at least one notch, a light-reflection layer is arranged at a surface of each notch, each notch connects an upper surface and a lower surface of the light guide plate body, and is of an arc shape, a surface of the notch is a cylindrical surface having a predetermined radian, and a tangential surface to the cylindrical surface is substantially parallel to a second surface of the wedge-shaped structure; a wedge-shaped structure is arranged on a lower surface of the light guide plate body and adjacent to a bottom of each notch; the wedge-shaped structure has a first surface attached onto the lower surface of the light guide plate body, the second surface serving as a light-entering surface, and a third surface intersecting the first surface and the second surface and having an acute angle relative to the first surface; both the second surface and the third surface are below the lower surface of the light guide plate body; a light-reflection layer is arranged on the third surface; a light source is arranged at a position on the lower surface of the light guide plate body adjacent to the second surface of the wedge-shaped structure; and a light beam from the light source passes through the light-entering surface and reaches the third surface of the wedge-shaped structure and the notch, so that the light beam is reflected by the light-reflection layer at the third surface and the light-reflection layer at the notch toward the light guide plate body. the light guide plate body is of a circular or near-circular shape; the light guide plate body is provided at a side portion at least one notch, a light-reflection layer is arranged at a surface of each notch, each notch connects an upper surface and a lower surface of the light guide plate body, and is of an arc shape, a surface of the notch is a cylindrical surface having a predetermined radian, and a tangential surface to the cylindrical surface is substantially parallel to a second surface of the wedge-shaped structure; a wedge-shaped structure is arranged on a lower surface of the light guide plate body and adjacent to a bottom of each notch; the wedge-shaped structure has a first surface attached onto the lower surface of the light guide plate body, the second surface serving as a light-entering surface, and a third surface intersecting the first surface and the second surface and having an acute angle relative to the first surface; both the second surface and the third surface are below the lower surface of the light guide plate body; a light-reflection layer is arranged on the third surface; a light source is arranged at a position on the lower surface of the light guide plate body adjacent to the second surface of the wedge-shaped structure; and a light beam from the light source passes through the light-entering surface and reaches the third surface of the wedge-shaped structure and the notch, so that the light beam is reflected by the light-reflection layer at the third surface and the light-reflection layer at the notch toward the light guide plate body.