Telecom operators are deploying the fifth generation (5G) networks around the world which promises high information transmission rate,wide net-work coverage,low communication delay,and easy access to a large number of devices.However,during the construction and operation of 5G,telecom oper-ators face many challenges,such as insufficient fre-quency resources,low efficiency of network manage-ment,information opacity,risks of data interoperabil-ity,and network privacy vulnerabilities.As 5G is gen-erally deployed in heterogeneous networks with mas-sive ubiquitous devices,it is quite necessary to pro-vide secure and decentralized solutions.Blockchain is a distributed system maintained by multiple par-ties with inherit features including decentralization,traceability and tamperproof.These features collec-tively contribute to a new application ecosystem where transactions are secure and trustworthy.Therefore,blockchain is expected to integrate with 5G networks to build safer and more reliable mobile network in-frastructures.This paper firstly discusses the merits of blockchain technology and the benefits of integrating it with 5G networks.Then a variety of applications of blockchain technology in telecom network opera-tion are reviewed,including spectrum sharing,interna-tional roaming settlement,network operation manage-ment,number selection management and supply chain management.In the end,we show our recently ad-vance in integrating blockchain in 5G by introducing a multi framework based blockchain service network architecture deployed in real environment.