A low-power fast-transient on-chip low-dropout regulator (LDO) using advanced reference buffer is presented in this paper. The advanced reference buffer is proposed to provide the reference voltage of the LDO with more accurate level to improve the regulation performances. Moreover, in order to suppress the undershoot, the advanced reference buffer increases the reference voltage of the LDO abruptly when the output voltage decreases during transient state. Hspice simulation results show that the proposed LDO could deliver 100-mA load current with 0.8-V output voltage and 200-mV dropout voltage. By only consuming 1.8-µA quiescent current at light load, the undershoot, the overshoot and the settling time of the proposed LDO for load current switching from 100 µA to 100 mA with 300-ns edge time are about 60 mV, 80 mV and 1 µs, respectively.