The invention discloses an engine valve collet dismounting and mounting auxiliary tool. The engine valve collet dismounting and mounting auxiliary tool comprises a screw, a fixing clamping base, a guiding block, a press-fitting mechanism and a support. The guiding block is mounted on the upper portion of the support. The fixing clamping base is mounted on the upper portion of the guiding block. The screw penetrates through the fixing clamping base and the guiding block in the vertical direction. The lower portion of the screw is connected with the press-fitting mechanism. A valve spring is pressed through the screw, when an heavy-duty diesel engine is maintained, the valve spring can be pressed easily, the dismounting and mounting operation of a valve collet is completed, meanwhile, the screw has the self-locking function, after pressing is completed, a maintenance man can conduct the dismounting and mounting operation with two hands, the operation efficiency is improved, the operationsafety is improved as well, the press-fitting mechanism can be adjusted according to valve rods of different types, and the application demands of the valve rods of different types can be met.