Abstract: With the rapid growth of medical data, how to realize the secure sharing of electronic medical data has become an urgent problem for electronic medical system. Therefore, a secure sharing scheme of electronic medical data based on blockchain is proposed to realize the secure sharing of electronic medical data between data holders and medical research institutions. The scheme used zero knowledge proof mechanism to verify whether the medical data of data holders met the needs of medical research institutions, and used homomorphic encryption technology to ensure the security of medical data and realize the operability of ciphertext. Theoretical analysis shows that the scheme can meet the security requirements of confidentialityand availability. Experimental results show that using this scheme to share electronic medical data requires lower computational cost.