With the rapid development of medical information, the medical cyber system is rapidly transforming, and medical information sharing faces new challenges. Blockchain technology is a revolutionary technology. It has the characteristics of tamper-proof and privacy-preserving, and has natural protection for big data systems, that can be used in medical systems. In this paper,we proposed to store medical cyber physical data in a mixed blockchain with private blockchain and consortium blockchain in order to realize the secure storage of medical cyber physical data by the tamper-resistant and sharing of blockchain technology. In the system, a threshold signature system based on blockhain is also proposed. Aiming at the situation that medical accidents are easy to occur in multidisciplinary joint consultation in the medical process, this paper proposes to use threshold signature for joint consultation. Using the security and threshold of threshold signature, treatment can be carried out when the threshold number is reached, and medical data can be uploaded to the consortium blockchain. The security analysis and performance analysis show that the scheme has advantages in safety and performance and is suitable for the medical environment to a certain extent.