Abstract：A new approach to design lithium battery circuit based on MCU was proposed. The method used 8-bit CMOS Flash MCU PIC16F886 as the master chip. In order to monitor the status of the circuit and protect the batteries, the circuit design should first contain a protection circuit with S-8254 chip, second a protection circuit with S-8244, third an MCU auxiliary protection circuit and fourth a battery equilibrium control circuit. The experiments were made based on the circuit design of lithium batteries. The results of the experiments show that the design not only accurately measured the battery pack, effectively protected the battery circuit, but also enabled a balanced charge of the battery, so that all batteries could give the best performance in order to satisfy the laptop back-up power requirement.