The present invention is to provide a real time clock charging circuit mounted on a circuit board, which comprising an booting power input terminal adapted to receive a booting power passed through a first control module to a power storage unit and a second control module; the power storage unit adapted to store the booting power and to output a spare power prohibited from flowing into the first control module and the spare power only flows into the second control module as receiving no input power; a standby power input terminal adapted to receive a standby power to the second control module enabling to output those power to the real time clock and avoiding them to transmit outside.