The present invention discloses a light guide plate and a backlight module having the same. The light guide plate includes a light emitting surface, a light incident surface, a light reflecting surface, and a plurality of prisms disposed on the light reflecting surface. The disposition direction of the prisms can be parallel or perpendicular to the lengthwise direction of the light reflecting surface. An inclined angle may exist between the disposition direction of the prisms and the lengthwise of the light reflecting surface. The backlight module includes a light guide plate, a light source, and an optical film set, wherein the light source is disposed near the light incident surface. The optical film set partially covers the light emitting surface, wherein a distance exists between a vertex of the prism and an edge of the optical film set.