A high efficiency capacitor-free low-dropout regulator (LDO) with the cross-couple class-AB push–pull input stage is presented for wireless internet of things and wireless senor network chip. Utilizing the proposed input stage, both load/line regulation and power supply rejection ratio (PSRR) are improved. Meanwhile, the transient response including the undershoot voltage, the overshoot voltage and the recovery time is optimized with the sub-threshold slew-rate enhancement circuit and the multiple loop compensation strategy. Simulation results show that the LDO only consumes a quiescent current of 41.8 μA, resulting in the energy efficiency of 99.96% at a 100-mA maximum load current (IL) from 1.2 V supply voltage using 0.18-μm CMOS process. When IL is switching from 0 A to 100 mA in 0.3 μs, the undershoot voltage and the overshoot voltage are about 131.62 mV and 126.31 mV while the corresponding recovery time are 0.77 μs and 0.55 μs with CL = 100 pF, respectively. Furthermore, PSRR at 1-kHz is boosted to − 58.8 dB at full load. Besides, an excellent line and load regulation of 0.24 mV/V and 1.76 μV/mA are obtained, respectively.