A rapidly assembled office desk is provided, wherein a leg and a front guard board of the office desk are respectively fixed through a hinge, so that the leg of the office desk is linked with the front guard board. An inner side of the front guard board of the office desk and a back face of the desk board of the office desk are respectively fixed through a slide rail device, so that the front guard board of the office desk is linked with the desk board. In this way, the front guard board can be unfolded or be folded for storage at the back face of the desk board, and the two legs can also be unfolded or be folded for storage at the inner side of the front guard board.