In the era of Internet of Things （IoT）， the integration of Artificial Intelligence （AI） and IoT has become a significant trend driving technological advancements and application innovations. With the exponential growth in the number of connected devices， enhancing end-users’ trust in intelligent systems has become especially critical. Explainable Artificial Intelligence （XAI） refers to AI systems capable of providing their decision-making processes and outcome explanations. The emergence of XAI has propelled the development of AI technology and increased users’ trust in AI systems. Therefore， a research review on XAI in IoT applications was performed. Firstly， the background and significance of IoT and XAI were discussed. Secondly， the definition and key technologies of XAI were presented. Thirdly， the recent progress in traditional AI-driven IoT applications as well as XAI-driven IoT applications were introduced. Finally， the future development directions of XAI in IoT applications were prospected and the associated challenges were summarized.