Change impact evaluation of complex product plays an important role in controlling change cost and improving change efficiency of engineering change enterprises. In order to improve the accuracy of change impact evaluation,this paper firstly expresses engineering changes based on multi-stage complex networks. Then, it constructs the evaluation index system of complex product engineering change impact. Next, based on the combination weighted three-parameter grey relational model, the engineering change impact of complex product is evaluated. Finally, a case analysis was carried out with the permanent magnet synchronous centrifugal compressor in a large permanent magnet synchronous centrifugal unit to verify the effectiveness of the proposed method.