With the rapid development of smart grid construction in many countries, the coverage of smart meters has been greatly improved, but how to ensure the accuracy of measuring the state of smart meters has become a problem for all power utilities. Power utilities usually replace old smart meters with new ones that have reached a certain running time. This replacement method will lead to the replace of some smart meters which can still work normally, resulting in a lot of waste. In order to solve this problem, this paper presents an online evaluation method for smart meters by analyzing their power acquisition data. The data about smart meters from advanced metering infrastructure and the data from smart meters themselves are studied in detail, and six sub-evaluation indicators including reliability, measurement abnormal events, smart meter events, overload, state of clock battery and regional index, that reflect the state of smart meters are extracted. The entropy weight method is adopted to fuse four of these indicators, then the state evaluation model is established based on the fuse of the the six sub-indicators. The model has been verified with actual data, and the results indicate that the state evaluation model can successfully distinguish the states of smart meters and promote more accurate replacement of smart meters to save the operating cost of electricity.