A highly reliable startup circuit based on current sampling and MOS switching is proposed to address the startup issues of a no-ground-on-chip three-terminal voltage regulator. A low-voltage design strategy was adopted, enabling a low dropout voltage. The circuit was designed and simulated using the CSMC 0.25 μm 60 V BCD process, and successfully underwent tapeout and testing. Simulation results showed that after implementing the proposed startup circuit scheme, the voltage regulator could start stably. The dropout voltage range of the regulator is 1.35 V to 35 V, and the maximum output current is 7.5 A. The temperature coefficients of the reference voltage and output voltage are 1.13×10^-5/℃ and 1.22×10^-5/℃, respectively. The voltage regulator exhibits good linear regulation and load regulation. Test results indicate that the designed high-reliability startup circuit enables the voltage regulator to start normally when powered on.