A novel dual-voltage pacing system for implant pacemaker is presented in this paper. In order to reduce supply voltage ripple and diminish process variation imposed on the divided-resistor, a fully on-chip low-dropout (LDO) regulator is proposed. Meanwhile, the adjustable pacing circuit together with a sense feedback is employed to deliver electrical stimuli of 16-step amplitudes to induce cardiac contraction. The pacing circuit with a LDO regulator was fabricated in TSMC 0.35-μm CMOS technology, consuming total power of 1.29 μW including 185 nA of ground current in 1.2-V LDO and having a power consumption of 30 nW in the 1-V pacing step controller. Experimental results demonstrate that the proposed LDO regulator features a powersupply rejection ratio (PSRR) of -30 dB with the output ripple of 570 μVpp under the input sinusoidal wave of 19.6 mVpp. Even with the load current up to 10 μA, LDO yields a line regulation that is less than 3% deviation.