The invention discloses a multi-operating-condition bearing type assembling and disassembling support of a numerical control machine tool additional main shaft. A fixed seat, a first connecting arm, a second connecting arm, a third connecting arm and a supporting seat in the assembling and disassembling support are in pin joint in sequence, the first connecting arm, the second connecting arm and the third connecting arm form a three-joint structure capable of being folded and unfolded, the three-joint structure can freely rotate to a preset assembling and disassembling position in the unfolding process, a double-connecting-rod bearing mechanism is mounted to carry out bearing and supporting according to assembling, disassembling and bearing requirements in the assembling and disassembling process of the additional main shaft, a transverse rod can be in pin joint with the inside of a first transfer barrel through a pin shaft, a longitudinal rod is optionally in pin joint with the inside of a second transfer barrel or the inside of a third transfer barrel or the inside of a fourth transfer barrel, the transverse rod and the longitudinal rod are respectively formed by sleeving a plurality of hollow joint rods and can be stretched out and drawn back freely, the double-connecting-rod bearing mechanism can carry out follow-up bearing along with the three-joint structure, and the assembling and disassembling operation of additional main shafts of different specifications is met. Compared with the prior art, the additional main shaft is convenient and easy to assemble and disassemble, manpower consumption is reduced, and assembling and disassembling efficiency is high.