The invention relates to a rapid assembly device for a crankshaft timing gear. The rapid assembly device comprises a crankshaft supporting and positioning mechanism and a press-fit mechanism. The crankshaft supporting and positioning mechanism comprises V-shaped blocks, a positioning seat, a positioning column and a compression cylinder. Main journals at the two ends of a crankshaft are correspondingly arranged on the V-shaped blocks. A first connecting rod journal of the crankshaft is arranged on the positioning seat, and the side face is pressed and positioned through the positioning column and the compression cylinder. The press-fit mechanism comprises a propelling air cylinder, a sleeve, a spindle, a connecting shaft and a compression spring. The spindle, the connecting shaft and the compression spring are mounted in the sleeve. The front end of the spindle extends out of the sleeve. Each of the front portion and the middle portion of the spindle is provided with a key groove. A flat key matched with a timing gear key groove is mounted in the front key groove. During assembly, the timing gear key groove is aligned with the flat key and arranged on the spindle, the propelling air cylinder is ventilated and drives a piston rod to move forwards and accordingly drives the sleeve and the spindle to move, and the timing gear can be quickly pressed into the journal at the front end of the crankshaft through the advancing sleeve and the spindle. The rapid assembly device has the beneficial effects of being reasonable in structure and easy to manufacture and assemble, and quick assembling of the timing gear can be achieved.