The invention discloses a medical 
data security sharing method based on a block chain and 
federated learning. The data applicant can use the data after being authorized on the chain of the 
data provider; the data 
fingerprint carries out hash abstract chaining on authorized data, the problem that the authorized data is maliciously tampered to cause data inconsistency is prevented, the use right ofthe 
original data is shared in the whole process, a data user cannot directly obtain the data, and the value of the data can be mined only through 
federated learning. In each round of iterative computation of 
federated learning, asset chaining is carried out on 
model parameters and aggregation results, and credible 
traceability of federated learning computation can be achieved. Each step of operation in the 
data sharing process is subjected to related auditing by a supervisor, such as identity auditing, data checking, transaction detail auditing and the like. According to the invention, aggregation calculation is carried out without the help of a central 
server, decentralized federated learning is realized, aggregation calculation is realized through an intelligent contract, and maliciousaggregation calculation results received by each node due to malicious control of the central 
server are avoided.