With a large number of mobile terminals accessing IoT for information exchange and communication, security issues such as identity authentication, data transmission, and device failure are becoming more and more serious. Most of the traditional security technologies are based on centralized systems, and due to the limitation of IoT topology, traditional security technologies can only be applied to specific industries. Blockchain technology has the features of decentralization, data encryption, and tamper-proof, which are especially suitable for application in complex heterogeneous networks. This paper discusses for the first time the use of the block chain in many fields, providing an opportunity to address IoT security issues. Second, it discussed the IoT acceptance on various domains and the privacy issues IoT faces on limited resources. Finally, this paper investigates many of the problems facing the integrated process of block chain-based and IoT-based applications. The purpose of this article is to provide an overview of block chain based policies for privacy protection in IoT. After analyzing related solutions, blockchain technology can work better in the area of IoT security and privacy protection