The invention provides an isolation type battery power supply scheme. A lithium battery, a resistor R1, a capacitor C1, a flyback isolation power supply chip, a transformer, an enable circuit, a clock power circuit and an alternating current mains supply circuit are adopted in the scheme. The scheme is characterized in that under the alternating current supply condition, the working voltage of the clock power circuit is provided by the alternating current mains supply circuit while the lithium battery only provides quiescent current for the flyback isolation power supply chip; under the alternating current outage condition, the lithium battery is used as a standby power supply by a system and provides the working voltage for the clock power circuit. Meanwhile, the power supply scheme has a lithium battery capacity detection function and sends out a battery replacement notice when the battery capacity is lower. With the adoption of the scheme, a lithium battery power supply system and a circuit of an alternating current mains supply system are isolated, that is, battery replacement electric shock hazards due to the fact that the battery power supply system is common-grounded with the alternating current mains supply system are avoided, and impact damage caused by direct connection of the battery with an MCU (micro controller unit) to MCU pins is also effectively avoided.