With the rapid development of wireless remote sensor systems, battery is becoming the limiting factor in the lifetime of the device and miniaturization. As a way to eliminate battery in the system, the conversion of ambient vibration energy has been addressed. The piezoelectric cantilever beam with a proof mass was exploited for energy conversion since it can generate large strain and power density. The design of cantilever beams was optimized through numerical analysis and FEM simulation at higher acceleration condition. The investigated parameters influencing the output energy of piezoelectric bimorph cantilevers include dimensions of cantilever beam and proof mass. The resonant frequency and robustness of cantilever structure were also considered for enhancing power conversion efficiency and implementing devices at high acceleration condition. The power density generated by the optimized piezoelectric device was high enough (> 1200 μW/cm3) to operate microsensor systems. However, high stress near clamping area of cantilever beam could lead to the fracture at high acceleration condition.