The overall, hardware and software design scheme of smart electricity meter based on NB-IoT is introduced, and a three-layer development framework for NB-IoT development is proposed. Several key technologies such as surge response, current and voltage sampling algorithm and harmonic measurement are studied, and improved algorithms are proposed. Compared with the data collected by standard meters, the designed smart electricity meters meet the requirements of accuracy, stable operation, low acquisition frequency, safe and reliable communication, and lower cost than similar electricity meters.