The growing demand for electricity has set higher requirements for the sensing and measurement system of smart distribution network. Therefore, a new state monitoring technology for power metering is proposed based on automatic sensing and measuring technique to improve power metering. Firstly, the influence of various physical conditions and natural environment is analyzed on power metering equipment. Then, internal detection is used to detect the operation state of the equipment. Secondly, DC (direct current) magnetic bias is detected by self-excited fluxgate. Furthermore, the working condition of the secondary circuit is tested by the secondary circuit current measurement method. Finally, the narrowband Internet of Things technology is adopted to conduct data communication with the terminal platform. The research results show that compared with the traditional online operation state detection and management system of smart distribution network, the innovative state monitoring technology can additionally monitor the temperature, DC magnetic bias and secondary circuit of the distribution network. This shows that improved monitoring technology based on automatic sensing and measuring technique can monitor the important state of the distribution network to reduce the risks caused by the inability to detect potential problems and improve the performance of the distribution network. The optimized state metering technology makes an example for the improvement of automatic sensing and measuring technique of the metering equipment of smart distribution network nationwide.