An optical fiber module rack system includes a rack including multiple accommodation chambers, opposing first and second sliding grooves located in each accommodation chamber, and a stop block located at each of opposing front and rear ends of each first sliding groove, and optical fiber storage boxes each including a box body mounted in one respective accommodation chamber, a first optical fiber module and second optical fiber module mounted in opposing front and rear sides of box body and connected together, two guide rails located at two opposite lateral sidewalls of box body and respectively coupled to first sliding groove and second sliding groove of respective accommodation chamber, two elastic retainer strips respectively extended from opposite ends of one guide rail and provided with a respective hook block for engagement with one respective stop block, and elongated press member extended from other guide rail for pressing by external force to disengage hook blocks from respective stop blocks for allowing removal of optical fiber storage box out of respective accommodation chamber.