Vibration energy harvesters (VEHs) can transform ambient vibration energy to electricity and have been widely investigated as promising self-powered devices for wireless sensor networks,wearable sensors,and applications of a micro-electro-mechanical system (MEMS).However,the ambient vibration is always too weak to hinder the high energy conversion efficiency.In this paper,the integrated frame composed of piezoelectric beams and mechanical amplifiers is proposed to improve the energy conversion efficiency of a VEH.First,the initial structures of a piezoelectric frame (PF) and an amplification frame (AF) are designed.The dynamic model is then established to analyze the influence of key structural parameters on the mechanical amplification factor.Finite element simulation is conducted to study the energy harvesting performance,where the stiffness characteristics and power output in the cases of series and parallel load resistance are discussed in detail.Furthermore,piezoelectric beams with variable cross-sections are introduced to optimize and improve the energy harvesting efficiency.Advantages of the PF with the AF are illustrated by comparison with conventional piezoelectric cantilever beams.The results show that the proposed integrated VEH has a good mechanical amplification capability and is more suitable for low-frequency vibration conditions.