Abstract: In order to evaluate the influence degree of BIM on the synergy ability in the assembly design stage of prefabricated buildings, based on the principle of synergistic order parameter, we establish a synergy measure model that takes the software synergy and professional coordination as the first-level indicator, and select 22 sub-orders indexes. Combined with a specific case, the design stage of prefabricated building is taken as the research object. In order to quantify the measurement indicators, the expert scoring method is used to evaluate and calculate the synergy ability of the constructed index system by efficiency function. The results show that due to the inconsistency of data sharing and conversion format between BIM software, information loss and low transmission efficiency still occur. There is also a certain gap between professional collaboration and ideal state. Further improvement are need for BIM technology development.