Cloud services can provide storage space,but a single cloud environment cannot provide secure data storage and sharing.However,the secure storage and sharing is an important content to ensure the security of medical data.Public audit technology protects cloud data from tampering,thus ensure the secure storage of medical data.The public access of the tamper-resistant blockchain can realize the secure sharing of medical data.The paper uses public audit technology to propose a blockchain-based cloud storage and sharing scheme for medical data,and analysis shows that the scheme is secure and effective.