The invention discloses a synchronizer assembly assembling mechanism. The synchronizer assembly assembling mechanism comprises a base, an installation sleeve and a supporting device arranged on the base, wherein the inner wall of the installation sleeve is provided with a plurality of special-shaped grooves which are evenly distributed in the circumferential direction, and the special-shaped grooves are matched with synchronizer sliding blocks. The installation sleeve rotates relative to the base, so that the synchronizer sliding blocks in the special-shaped grooves are compressed. The supporting device elastically supports a synchronizer gear sleeve and a synchronizer gear hub, when pressure is exerted in the axial direction, the synchronizer gear sleeve and the synchronizer gear hub change in displacement in the axial direction, and the compressed synchronizer sliding blocks, the synchronizer gear sleeve and the synchronizer gear hub are assembled. According to the synchronizer assembly assembling mechanism, the synchronizer sliding blocks are compressed in advance, so that during assembling, the synchronizer sliding blocks can slide into the synchronizer gear sleeve without resistance, assembling is carried out directly, and the situation that the synchronizer sliding blocks are popped out or damaged due to improper force exertion is avoided; and moreover, the multiple synchronizer sliding blocks can be installed at the same time, operation is easy and convenient, labor is saved, and the assembling efficiency is high.