In order to solve the problems of slow accurate search speed due to mixed data storage and difficult security governance caused by unclassified and graded data management， a data classified and graded access control model based on master-slave multi-chain was built to achieve classified and graded protection of data and dynamic secure access. Firstly， a hybrid on-chain and off-chain trusted storage model was constructed to balance the storage bottleneck faced by blockchain. Secondly， a master-slave multi-chain architecture was proposed and smart contracts were designed to automatically store data with different privacy levels in the slave chain. Finally， based on Role-Based Access Control， a Multi-Chain and Level Policy-Role Based Access Control （MCLP-RBAC） mechanism was constructed and its specific access control process design was provided. Under the graded access control policy， the throughput of the proposed model is stabilized at around 360 TPS （Transactions Per Second）. Compared with the BC-BLPM scheme， it has a certain superiority in throughput， with the ratio of sending rate to throughput reaching 1∶1. Compared with no access strategy， the memory consumption is reduced by about 35.29%； compared with the traditional single chain structure， the memory average consumption is reduced by 52.03%. And compared with the scheme with all the data on the chain， the average storage space is reduced by 36.32%. The experimental results show the proposed model can effectively reduce the storage burden， achieve graded secure access， and suitable for the management of multi-class data with high scalability.

The emergence of edge computing has expanded the scope of Internet of Things （IoT） cloud-terminal architecture. With the reduction of transmission and processing delays of massive data on terminal devices， it also brings new security issues. Aiming at the problem of data security and management issues between edge nodes of IoT and massive heterogeneous devices， and considering that blockchain technology is widely used in the security management of data in distributed systems， an IoT access control model Smart Contract for Attribute-Based Access Control （SC-ABAC） was proposed based on blockchain and edge computing. Firstly， an IoT access control architecture integrated with edge computing was proposed， and by combining smart contracts with Attribute-Based Access Control （ABAC）， SC-ABAC was proposed and designed. Then， the optimization of Proof of Work （PoW） consensus algorithm and the access control management flow of SC-ABAC were given. Experimental results show that the time consumed by the proposed model increases linearly with the number of times under continuous access to the block， the Central Processing Unit （CPU） utilization rate is stable， and the CPU security is good during the continuous access process. In this model， the time consumption of calling contracts in the query process only increases linearly with the times， and the time consumptions of the strategy addition and judgment process are both constant. And the optimized consensus mechanism has about 18.37 percentage points less time consumption than PoW consensus per 100 blocks. Therefore， the proposed model can provide decentralized， fine-grained and dynamic access control management in the IoT environment， and can reach consensus faster in a distributed system to ensure data consistency.