In architecture of cloud storage, the deduplication technology encrypted with the convergent key is one of the important data compression technologies, which effectively improves the utilization of space and bandwidth. To further refine the usage scenarios for various user permissions and enhance user’s data security, we propose a blockchain-based differential authorized deduplication system. The proposed system optimizes the traditional Proof of Vote (PoV) consensus algorithm and simplifies the existing differential authorization process to realize credible management and dynamic update of authority. Based on the decentralized property of blockchain, we overcome the centralized single point fault problem of traditional differentially authorized deduplication system. Besides, the operations of legitimate users are recorded in blocks to ensure the traceability of behaviors.