The invention provides a complex shared space assembling building decoration construction method based on BIM (building information modeling). The method comprises the following steps that (1), three-dimensional scanning is conducted on a construction site, and three-dimensional data of the construction site are collected; (2), a three-dimensional model is obtained according to the three-dimensional data; (3), a decoration model is built according to drawings; (4), the decoration model is matched to the three-dimensional model to conduct simulation installation, a collision test is conducted, discrepant areas and size deviation between the decoration model and the three-dimensional model are found out, and a collision result is obtained; (5), the decoration model is adjusted according to the collision result; and (6), coordinate installation point location information is extracted in a finished decoration model, the point location information is guided into a total station, and a line of a later-installed face is paid off. According to the complex shared space assembling building decoration construction method based on the BIM (building information modeling), the technical problems that in the prior art, building decoration construction deviation is troublesome to be adjusted, and construction efficiency and the construction quality are low are solved.