The smart meter clock battery can provide power for the clock chip in the meter during the power down state, and premature undervoltage of the clock battery is one of the common faults of the meter in recent years. To this end, through the analysis of the constant temperature degradation data of the clock battery, an empirical method to test and predict the battery power in the meter is proposed. Then, based on the domestic new dual?core smart meter with operating system, a management core operating system application is design for on?line power monitoring of the clock battery in the meter. This application regularly detects the battery power of the clock, gives an approximate battery life estimate, and reports abnormal conditions. The experimental analysis shows that the application can effectively monitor the battery capacity.