SouthEX is the first distributed exchange based on EOS. It adopts the mixing techniques of combining on-chain smart contract and off-chain matchmaking engine. In placing an order, the user pays the order amount with wallet directly. The on-chain smart contract escrows the order amount, and the off-chain matchmaking engine matches the order efficiently(as fast as millions of orders per second). Moreover, it employs on-chain and off-chain dual verification. After closing the deal, the smart contract will transfer the amount to wallet directly. In realizing the efficient matchmaking efficiency of the centralized exchange, SouthEX can dramatically reduce the quantity and time of the encrypted currency the user escrows in the exchange as well at the same time, so as to balance high efficiency and security.