The promotion of 5G provides new opportunities for the rapid development of the smart home industry, while the authentication issue of smart home systems has become a concern. The traditional centralized management and authentication methods adopted by smart home systems face centralized trust issues, and have the disadvantages of high performance overhead. Blockchain technology has become a research hotspot due to its advantages of decentralized and non-tampering features, providing new ideas for the realization of security certification for distributed smart home. Nevertheless, it also faces two challenges: the efficiency of user authentication with multiple distributed terminals and the leakage of user privacy. This study proposes a dynamic trusted lightweight authentication mechanism (DTL) based on blockchain. DTL uses consortium blockchain to build a blockchain system, which not only ensures that only authorized smart home sensor nodes can join the network, but also meets the needs of distributed security and scalability. DTL can achieve the following two advantages. (1) Aiming at the issue of authentication efficiency, by improving the consensus algorithm, a dynamic trusted sensor group (DTSG) authentication mechanism for smart homes is established, which avoids low access efficiency and low user access rate caused by one-to-one frequent authentication between the user and sensor terminal or gateway node. DTL has realized lightweight authentication. (2) For addressing the problem of user privacy protection, an authentication scheme combining DTSG mechanism and zero-knowledge proof is innovatively designed, which realizes user identity authentication without leaking user privacy. These security features are demonstrated by carrying out security analysis. Meanwhile, extensive simulations are conducted to validate the practicality and lightweight of DTL.