With the development of 5G-Advanced (5G-A) technology, the number of Internet of Things (IoT) devices has increased dramatically. Traditional centralized identity authentication and access control methods face severe challenges. Against this background, our paper proposed a cross-domain access control scheme for the IoT based on blockchain identity identification technology. By combining blockchain technology with the distributed Capability-based Access Control (CapAC) model, a unique capability token structure and storage method are designed. Smart contracts are used to manage tokens, and access control decisions are made based on blockchain transaction verification. Experimental verification shows that this scheme can effectively resist various attacks, make secure and accurate access decisions in large-scale IoT scenarios, and has stable performance, providing a reliable solution for cross-domain access control in the 5G-A era of the IoT.