Abstract: Given that existing centralized medical data management systems are vulnerable to hacking, internal leakage and tampering, and patients have no control over medical data, data between medical institutions cannot be interoperated, leading to cases of rediagnosis and misdiagnosis. On this basis, we propose a secure medical data sharing scheme using a combination of blockchain technology and improved proxy re-encryption technology, and build an access control mechanism using smart contracts to realize a patient-centric medical data security sharing mechanism. The experimental analysis shows that this solution can simultaneously meet the five major security properties (confidentiality, integrity, non-repudiation, privilege control and authentication) and improve the efficiency by about 19.45 percentage points compared with the comparison solution.