Abstract: Aiming at the problems of low transaction efficiency， high handling fee， and difficulty in the expansion of existing decentralized cross chain exchange schemes， a cross chain exchange based on smart contract(CCE-SC)is proposed. The protocol uses smart contracts to ensure the decentralization and security of cross chain exchange. It implements low-cost and efficient cross-chain transactions through three algorithms， i.e.， strategy formulation， strategy synchronization， and blockchain consensus verification. Each chain in the protocol only needs to deploy a smart contract that includes pool module， record management module， chain relay module and oracle module to realize cross chain exchange across multiple chains. The performance of the protocol is analyzed through experimental tests. The experimental results show that the protocol greatly improves the efficiency of cross chain exchange and reduces the handling fee overhead.

Key words: cross chain exchange; smart contract; decentralized; blockchain; protocol