In this paper, the compensation of internal resistance of the Li-Ion battery is proposed. The requirement of fast and steady charger becomes the most important issue for power management ICs. Refer to the characteristics of the battery, how to charge the battery with adequate current and fasten the time of charging is critical to the devisers. Due to the impedance of battery pack, the energy of charger charged to cell is consumed in it partly. As a result, the efficiency of charger is reduced inevitably. The previous design has proposed a dynamic circuit for reducing time . However the technique demands the external device to compensate the defeat. Thus, this paper extends the period of the CC mode to charge the battery with a faster speed. Owing to the shifting voltage on the reference voltage, the charger can delay the time that the operation mode from CC mode to CV mode. That is a fast-charging charger can be achieved by a large constant current stored in the battery during a long constant current period. Simulation results verify the success of the fast-charging technique due to the internal resistance compensation.