Abstract: In recent years, the application of artificial intelligence (AI) and blockchain technology in Internet of things (IoT) has attracted great attention and in-depth research in academia and industry. Blockchain technology has the characteristics of decentralization, anonymity, transparency and tamper-proof, but it needs improvement in terms of scalability, energy consumption and security. As a powerful analysis and decision-making tool, AI technology can predict and analyze data and make optimizations in real-time, however, the centralized structure, security and trustless has brought great limitations to its wide application. Therefore, in the IoT scenario, applying two technologies and integrating their respective advantages has become the focus of current research. This paper proposed a systematic review of the integration of blockchain and AI empowering IoT scenarios. First, it elaborated and analyzed the AI-assisted blockchain and the blockchain-based AI, respectively. Then, the state-of-the-art and related features applied in IoTs were systematically elaborated. Finally, some challenges and development trends in the future were discussed.