The invention discloses a press mounting device for multicylinder crankshafts, which is used for mounting the multicylinder crankshafts together by pressing and comprises a base (1), a lower press mold (2) arranged on the base (1), a mold shank base (12) connected with a press machine, and an upper press mold (6) that is opposite to the lower press mold (2) and is connected with the mold shank base (12), wherein a first locating pin (8a) matched with a small head hole of a connection rod is arranged on the lower press mold (2); a second locating pin (8) is arranged on the upper press mold (6); and a predetermined phase angle is formed between the first locating pin (8a) and the second locating pin (8). Two crankshaft assemblies to be pressed are positioned by the matching of the small head hole of the connection rod and the locating pin (8a) before the pressing operation is conducted, the phase angle between the two crankshafts is the predetermined phase angle, and the requirement that the tolerance of the phase angle after the multicylinder crankshafts are mounted by pressing is less than 30' can be met by adjusting the predetermined phase angle between the locating pins.