Blockchain has the characteristics of tamper-proof, traceability and trusted interaction, which can make up for some existing defects of the Internet of Things (IoT), such as single point of failure and data out of control caused by centralized management. The blockchain Internet of things (BIoT) has become a hot research field. However, the introduction of blockchain in the IoT scenario has also brought new privacy issues, including the disclosure of user data and transaction records. This paper firstly summarizes the role of blockchain in the current Internet of things scenarios, and proposes a BIoT model applicable to most Internet of things scenarios. Then, on this model, the corresponding privacy-preserving mechanism is proposed for the two application scenarios of micropayment and data interaction. Finally, the validity and privacy of the proposed mechanisms are verified by mechanism analysis and experiments, and the experimental results show that the proposed mechanisms have a short algorithm execution time and only generates a small amount of data.