Considering different blockchains being isolated and the data interaction and sharing difficulties in the current rapid development process of blockchain technology， a cross-chain mechanism based on Spark blockchain was proposed. Firstly， common cross-chain technologies and current mainstream cross-chain projects were analyzed， the implementation principles of different technologies and projects were studied， and their differences， advantages and disadvantages were summarized. Then， using the blockchain architecture maned main-sub blockchain mode， the key core components such as smart contract component， transaction verification component， transaction timeout component were designed， and the four stages of cross-chain process were elaborated in detail， including transaction initiation， transaction routing， transaction verification and transaction confirmation. Finally， the feasible experiments were designed for performance test and security test， and the security was analyzed. Experimental results show that Spark blockchain has significant advantages compared to other blockchains in terms of transaction delay， throughput and spike testing. Besides， when the proportion of malicious nodes is low， the success rate of cross-chain transactions is 100%， and different sub chains can conduct cross-chain transactions safely and stably. This mechanism solves the problem of data interaction and sharing between blockchains， and provides technical reference for the design of Spark blockchain application scenarios in the next step.

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.