A backlight module includes a light guide plate with a main body and a light source with a circuit board and a plurality of light bars. The main body has a light incidence surface and a light emitting surface. The light incidence surface has a plurality of accommodating grooves and the light emitting surface or the light incidence surface has a plurality of light-separation grooves which are perpendicular to the accommodating grooves. The accommodating groove has a first and a second light incidence parts. A reflecting layer is disposed on the surface of the circuit board being located between each two light bars. The light source is disposed on the light incidence surface and light bars are disposed for the accommodating grooves so as a predetermined distance located between the light bar and the second light incidence part is formed a light mixing space to reduce the production of bright lines.