The invention discloses a bearing support joint structure and an assembling method. The bearing support joint structure comprises multiple vertical rods, transverse rods and fixing blocks, wherein the vertical rods are parallel to one another, the transverse rods are perpendicular to the vertical rods, and the transverse rods and the vertical rods are connected through the fixing blocks. The vertical rods are arranged outside round steel bars of the fixing blocks in a sleeving manner and contacted with flat cubic steel blocks, so that horizontal displacement and rotation of the vertical rods can be effectively limited; by means of integral welding of the transverse rods and the fixing blocks, horizontal displacement of the transverse rods can be limited, meanwhile, the number of members of the support is reduced, and management is convenient; the fixing blocks serving as assisting parts for connecting the vertical rods and the transverse rods can be separated from the vertical rods, the vertical rods and the transverse rods are produced by meeting specifications of step pitch and span required by engineering practice, and accordingly, space can be saved during stacking or transporting of the vertical rods and the transverse rods.