In recent years, with a large number of devices that continuously join the IoT, data sharing as the main driver of the IoT market has become a research hotspot. However, the users are reluctant to participate in data sharing due to the security concerns and lacking of incentive mechanism in current IoT. In this context, blockchain is introduced into the data sharing of IoT to solve the trust problem of users and provide secure data storage. However, in the exploration of building a secure distributed data sharing system based on the blockchain, how to break the inherent performance bottleneck of blockchain is still a major challenge. For this reason, the efficient blockchain-based data sharing incentive scheme is studied for IoT, in which an efficient data incentive sharing framework based on blockchain is proposed, named ShareBC. Firstly, ShareBC uses sharding technology to build asynchronous consensus zones that can process data sharing transactions in parallel and deploy efficient consensus mechanisms on the cloud/edge servers and asynchronous consensus zones in sharding, thus improving the processing efficiency of data sharing transactions. Then, in order to encourage IoT users to participate in data sharing, a sharing incentive mechanism based on hierarchical data auction model implemented by smart contract is presented. The proposed mechanism can effectively solve the problem of multi-layer data allocation involved in IoT data sharing, and maximize the overall social welfare. Finally, the experimental results show that the proposed scheme is economically efficient, incentive-compatible, real-time, and scalability, and has low cost and good practicability.