Piezoelectric energy-harvesting technology is a critical solution to the power supply challenges of wireless sensor nodes. To address the limitations of conventional straight-beam piezoelectric energy harvesters，such as their high resonant frequency and low output power，we designed and investigated wedge-shaped beam structures using finite element simulations. A static mechanical comparative analysis was conducted to evaluate the stress distribution on piezoelectric materials in different wedge-shaped beams and traditional straight-beam structures. Modal analysis was performed on the wedge-shaped beam to elucidate the relationship between the structural parameters and resonant frequency. Finally，the power-generation performance of the wedge-shaped piezoelectric energy harvesters was systematically studied. The results indicated that the wedge-shaped structure with a linear increase in thickness from the fixed end to the free end exhibited lower resonant frequencies，which could result in a larger stress distribution within the piezoelectric material. Under a 0.5 g excitation level，the maximum output power of the tapered-beam piezoelectric energy harvester reached 1.6 times that of the corresponding traditional straight-beam structure.