The disclosure provides a mobile terminal and a method for controlling a battery thereof, wherein the mobile terminal includes: a main battery configured to supply power to the mobile terminal, a standby battery and a control device. Wherein the control device is configured to switch on the standby battery to supply power to the mobile terminal when the mobile terminal loses the enough power provided to the mobile terminal by the main battery. With the disclosure, a mobile terminal is allowed to be powered by a standby battery when a main battery fails to supply power, which avoids the inconvenience caused by lower battery power and improves the user experience of the mobile terminal.