Based on SMIC 0.18μm standard CMOS technology, an input-powered vibrational energy harvesting interface circuit is proposed. It can be applied in energy harvesting devices for the extremely low voltage and high conversion rate. The simulation results show that the minimum input voltage could be as low as 0.15V by utilizing bulk-driven technique. Correspondingly, the voltage conversion efficiency can reach up to 80%. And the power conversion efficiency is also 80% when voltage equals to 0.25V. The proposed input-powered interface circuit, compared with the conventional output-powered circuits, can automatically shut down when the input voltage amplitude is low enough, thereby avoiding unnecessary energy loss.