To improve the transient characteristics of the output-capacitor less low-dropout linear regulator （LDO）， a load detection circuit and overshoot/undershoot suppression circuits are designed and optimized to realize a output-capacitor less LDO with low power consumption and high transient characteristics. By utilizing the high-proportion current mirror to sample and follow the change of the LDO load current， the load detection circuit can adaptively change the tail current of the error amplifier to improve the system’s bandwidth and slew rate， thereby enhancing the transient response speed of the LDO. When overshoot occurs in the output voltage， the overshoot suppression circuit utilizes the high-pass network to detect the change of the gate voltage of the power transistor， enabling a discharge path for the load current to reduce its change in the output stage， so as to suppress the overshoot. When the output voltage undershoot occurs， the undershoot suppression circuit can rapidly increase the output current of the power transistor by opening the discharge path for the gate-drive current of the power transistor， and then effectively suppress the undershoot. Based on 0.5 μm CMOS process， the circuit is designed and tested. The results show that the input voltage of the LDO is 2~5.5 V， and the output voltage is 1.2 V； the maximum load current is 150 mA， with the linear regulation of 1.7×10-3； when there is no load， the quiescent current is less than 6.16 μA； when the load current varies in 1~150 mA@ 1 μs， both the undershoot and overshoot voltages are less than 300 mV. The LDO has the advantages of low power consumption and high transient characteristics， which can meet the application needs of portable electronic devices.