The invention discloses a light guide unit comprising a light guide plate and a plurality of cylindrical lenses. The light guide plate is provided with a first surface, a second surface relative to the first surface and a light incident surface for connecting the first surface and the second surface, wherein the light guide plate is provided with a plurality of disperse screen dots which are positioned on the second surface. The cylindrical lenses are configured on the first surface; each cylindrical lens extends along the first direction and is provided with a curved surface bent in the second direction. The cylindrical lenses are arrayed along the second direction. The pitch of adjacent disperse screen dots in the first direction is smaller than that in the second direction. The invention also discloses a backlight module using the light guide unit.