Due to the lack of physical protection for smart meters (SM) in advanced measurement system (AMI), and a large number of sensitive data will be generated. However, the existing security protection methods can not meet the security requirements of AMI. Therefore, a security protection method for smart terminals and smart meters based on blockchain is proposed to protect SM from network attacks. Firstly, the "cloud edge end" AMI system architecture, which is composed of massive SM, smart terminals (edge computing nodes) and cloud master station, is constructed to realize the local marginalization of most of the data. Then, the link fingerprint is formed by quantifying SM data, and then encoded and transmitted to the smart terminal of the station area, which integrates the credit consensus mechanism to preliminarily analyze the data and strengthen the security protection of AMI. Finally, all smart terminals are regarded as blockchain nodes, and the key information of each SM is taken as the transaction information of blockchain, so as to realize the reliable management of key and data based on blockchain. The received signal strength indicator (RSSI) values obtained by MICAz motes micro wireless measurement system are analyzed based on MATLAB. The results show that when there is network attack in AMI, its Pearson coefficient is negative or approximately zero, and the change of RSSI is no longer linear. Compared with other methods, the proposed method has the least energy consumption and the best security performance.