Focused on the issue that different blockchains are independent from and difficult to communicate with each other， a new type of permissioned public blockchain architecture of "main chain + sub chain" was proposed. Firstly， based on the existing algorithms such as Delegated Proof Of Stake （DPOS）， Verifiable Random Function （VRF） and Practical Byzantine Fault Tolerance （PBFT）， an innovative two-layer consensus algorithm was designed. And a trusted permission mechanism was added to make the blockchain have both permission and public characteristics. Secondly， the design process of the main and sub chains was described in detail. The management of the chain group and public services was provided by the main chain， while the sub chains were designed independently for different business scenarios， and cross-chain data communication was realized by connecting the main chain relay， thereby realizing the data secure isolation. Finally， an experimental environment was built for testing to verify the feasibility of the permissioned public blockchain design. Experimental results show that compared with some existing blockchains such as the Hyperledger Fabric， the proposed permissioned public blockchain has significant advantages， including a throughput of up to 25 000 times per second and an average delay time of about 8 s. It can be seen that this permissioned public blockchain provides technical support for further research on cross-chain data interconnection of different types of blockchains.