The invention relates to a press-fitting machine for a variable-center-distance auxiliary box spindle and an intermediate shaft bearing. A lifting mechanism is installed on the lower portion of a lathe bed and drives a working framework to ascend and descend. A double-layer conveyor line penetrates through the working framework. A plurality of press-fitting mechanisms are installed on the top of the working framework. The middle press-fitting mechanism is directly installed on the working framework. The press-fitting mechanisms on the two sides are respectively connected with a mobile variable-distance mechanism. The mobile variable-distance mechanisms comprise transposition sliding blocks, transposition guide rails and transposition cylinders. The transposition guide rails are installed on the working framework. The press-fitting mechanisms on the two sides are connected with the transposition guide rails respectively through the transposition sliding blocks and are driven by the transposition cylinders to reciprocate along the transposition guide rails. The press-fitting mechanisms comprise press-fitting oil cylinders, pressure sensors, pressure heads and displacement sensors. The pressure sensors and the pressure heads are sequentially connected with the output ends of the press-fitting cylinders. Each displacement sensor is installed on one side of the corresponding press-fitting oil cylinder. The press-fitting machine for the variable-center-distance auxiliary box spindle and the intermediate shaft bearing is driven by a pneumatic system, so that the center distance of the pressure heads is varied, and multiple products can share one device.