Abstract: The ERP (Earth rotation parameters) obtained by different technologies and different analysis centers are often different. In order to provide unified ERP for users, it is often necessary to fuse the ERP by using a special method. In this paper, an additional boundary constraints and internal constraints fusion model based on the ERP results of multi-analysis center is proposed. Firstly, all the analysis center results are converted to the same time by using the parameter transformation model and the boundary constraints are applied to the same characteristic points on the boundary point of the adjacent observation period. Then the inner constraints of the transformation parameters are applied to the long-term solutions of the analysis centers, and the fusion solutions of the ERP are obtained. Using SINEX (solution independemt exchange format) files from seven GNSS (Global Navigation Satellite System) analysis centers of six years from 2005 to 2011, their results are integrated and analyzed. Compared with the results of IERS C04 (International Earth Rotation and Reference Systems Service Combined 04), the results of the fusion method proposed in this paper have been significantly improved.