Abstract: Energy storage equipment is of great significance for smooth load and reliability improvement of microgrid. Charging and discharging loss is a key indicator characterizing the operation status and remaining life of microgrid energy storage equipment. Obtaining the characteristics of energy storage charging and discharging energy loss is crucial for evaluating their health status. Combined theoretical analysis with on-site operation data of energy storage equipment, a status evaluation method based on the charging and discharging energy loss characteristics of energy storage batteries is studied. Firstly, the energy loss sources of typical microgrid energy storage stations are analyzed, and the physical significance of energy loss during charging and discharging is clarified. Based on the life curve of existing batteries, the influence of temperature and discharge depth is then analyzed, and it is proposed to characterize the loss characteristics through energy loss rate. Based on actual on-site operation data of energy storage equipment, it is found that the cumulative loss rate and monthly loss rate exhibit a clear pattern. The cumulative loss rate slowly increases and tends to saturation. The monthly loss rate has obvious seasonal characteristics, and the loss rate from May to August is higher than other months, which is related to the ambient temperature. A strategy for online intelligent evaluation of equipment status based on energy storage charging and discharging losses is proposed. Considering reducing energy losses to extend equipment service life and improve utilization, it is suggested to maintain a certain depth of charging & discharging and full charging & full discharging times during equipment operation.