A frame assembly for installing panel modules with different dimensions is disclosed. The frame assembly includes a first frame and a second frame. The first frame has a first fixing structure formed thereon and a first sliding structure in an axis direction. The second frame has a second fixing structure formed thereon and a second sliding structure in the axis direction. The second sliding structure is slidably engaged with the first sliding structure. The first fixing structure and the second fixing structure are fixed on a side of a first panel module or on a side of a second panel module when the second frame slides relative to the first frame in the axis direction to a first position or to a second position.