Traditional multi-level security (MLS) sys-tems have the defect of centralizing authorized facil-ities, which is difficult to meet the security require-ments of modern distributed peer-to-peer network ar-chitecture. Blockchain is widely used in the field of access control with its decentralization, traceabil-ity and non-defective modification. Combining the blockchain technology and the Bell-LaPadula model, we propose a new access control model, named BC-BLPM, for MLS environment. The“multi-chain”blockchain architecture is used for dividing resources into isolated access domains, providing a fine-grained data protection mechanism. The access control poli-cies are implemented by smart contracts deployed in each access domain, so that the side chains of differ-ent access domains storage access records from out-side and maintain the integrity of the records. Finally, we implement the BC-BLPM prototype system using the Hyperledger Fabric. The experimental and analyt-ical results show that the model can adapt well to the needs of multi-level security environment, and it has the feasibility of application in actual scenarios.