As a promising Internet censorship circumvention technique, refraction networks have attracted the wide attention of researchers in recent years. However, it remains a crucial issue to be tackled, i.e., how to motivate more service providers, known as decoy routers, and clients to join refraction networks, especially with guaranteed security and privacy. To address the issue, we develop a decentralized service auction framework based on the blockchain constructed through clients and decoy routers. Further, we design a multi-stage service auction (MSSA) smart contract composed of multiple functions and events, which are triggered and executed autonomously to complete the tasks, including registration, double auction, first-price sealed auction, and payment clearing. Moreover, we implement the designed MSSA smart contract in the Remix integrated development environment and run a test case on Ethereum virtual machines. The experiment results verify the modest gas and ether cost of the smart contract-based solution and its effectiveness.