An ultra-low power fast transient response NMOS LDO with adaptive charge pump was designed. The whole circuit mainly included an error amplifier module, a buffer module, a power stage, a dynamic zero module and an adaptive charge pump module. The adaptive charge pump could adjust the operating frequency according to the size of the load current. It ensured the ultra-low power consumption under light load conditions while taking into account the requirements of the gate of the power transistor under heavy load conditions. At the same time, in order to meet the needs of fast transient response in the circuit, a dynamic current circuit was added. The circuit was designed in a BCD 0.18 μm process. Its working voltage range is 2.5-3.6 V, the output voltage is 1.2 V, the load range is 10 μA-20 mA, and the working temperature range is -40-125 ℃. The simulation results show that the designed LDO power supply voltage regulation rate can reach 1.123 mV/V, the recovery time of heavy load jumping to light load and the recovery time of light load jumping to heavy load are 260 μs and 5 μs respectively, while the minimum quiescent current is only 0.291 μA.