The utility model discloses a detecting method of battery capacity, comprising the following steps: smoothed value of battery voltage can be get through wave filtering of sampling value of the battery voltage; current battery threshold is confirmed according to the prior business mode; promoting information is done according to the comparison result for the smoothed value of battery voltage and the battery threshold and the information is used for promoting current battery capacity. The utility model has the advantages of more accurately weighing rest capacity of the battery, remedying the failure that the rest capacity of the batter is confirmed through only using single sampling value of the battery voltage and single battery threshold for prior art and bringing good using experience for users through the embodiment, current battery threshold which is confirmed according to current business mode and current battery capacity which is get through comparison between the smoothed valve of the battery voltage and the battery threshold through wave filtering of a plurality of sampling value for battery voltage.