In order to realize the secure storage, management and access control of medical data, this paper proposes a medical data sharing system based on blockchain, Internet of Things, cloud storage and proxy re-encryption algorithm. The system is divided into system management layer, data collection layer, block chain network layer, cloud service layer and application layer. The working process of the system is analyzed, including system initialization, data collection and upload, data query and sharing. The proposed medical data sharing system based on block chain is simulated and tested. The simulation results show that the scheme provides a reference for data security management and reliable operation of intelligent medical system.