A capacity judgment module and a capacity calibration method thereof are disclosed. The capacity judgment module is used to judge a capacity of a battery installed in an electronic device. The capacity judgment module includes a database, a voltage detection module and a processing module. The database is used to store the voltage-capacity comparison curve. The voltage detection module is used to obtain a voltage value interval between a maximum use voltage value and a minimum use voltage value of the electronic device so as to divide the voltage value interval into a plurality of levels. The processing module is used to query the voltage-capacity comparison curve to actually modify the plurality of levels of the voltage value interval of the electronic device and the battery capacity ratio according to the voltage-capacity comparison curve, thereby creating a new voltage-capacity comparison table,