Aiming at solving the inefficiency and flexibility issues of access control and preventing the security in access control contracts, a blockchain-based dynamic access control model of user roles and entity attributes based on big data cloud storage and BBAC-BDCS, is proposed. The access control strategy is stored in the blockchain through smart contracts, where agencies assign roles to relevant users. They obtain access rightsbased on credit and use metadata to query and parse data with public and private chains. The two-layer structure involves the access control calculation method of smart contracts to achieve access control of big data cloud storage resources. Experimental results show that this model makes a contribution by guaranteeing users secure, dynamic, and fine-grained access control, especiallywhen accessing data in a big data cloud storage environment.