A window blind system includes a top traverse supporter adapted for affixing to a top beam of a ceiling, and two shading arrangements downwardly extended from the top traverse supporter The first shading arrangement includes a base member, a plurality of slats, a first hanging system for spacedly and suspendedly supporting the slats and for controlling a tilt angle of each of the slats, and a first operating system for selectively lifting up the base member towards the top traverse supporter and unlifting the base member to drop downwardly away from the top traverse supporter. The second shading arrangement includes a second hanging system suspendedly support a predetermined set of the slats, so that by lifting up the second hanging system, the predetermined set of the slats are capable of being lifted for selectively allowing a light of desirable intensity passing through.