Blockchain refers to the technical scheme of collectively maintaining a reliable database through decentralization and distrust. It is known as the symbol of the fourth industrial revolution after steam, electricity and computers. It has many characteristics, such as reliability and usability. The design of blockchain enables it to effectively prevent failures and attacks. Because the open user group enjoys the blockchain, there is no system caused by a single fault. If any node in the network fails, other participants can still run as usual, which ensures the reliability and accessibility of information. Transparency-any network node can observe the transaction history on the blockchain, so the blockchain has high auditability and trust. Invariance-unconsciously