The energy conversion model of the piezoelectric cantilever beam (piezoelectric beam) under displacement excitation in the fixed end was established according to Hamilton principle to study the influence of structural parameters, material properties as well as excitation frequency of the piezoelectric beam on energy generation by using the method of numerical simulation and experimental testing. The research results showed that there were optimal thickness ratios (OTRs) respectively for the piezoelectric monomorph cantilever beam generator and piezoelectric bimorph cantilever beam generator to obtain maximal electrical energy in the same metal plate materials. With the increasing of the Young’s modulus ratio, the OTRs of the two generators decreased in different metal plate materials. When copper and molybdenum plates were used as the substrates, the monomorph and the bimorph cantilever beams achieved the OTRs of (0.7, 0.35) and (0.45, 0.2), respectively. In the same thickness ratio (0.5) and external excitation condition, the Young's modulus showed different influences on energy generation of the two generators. By adjusting the quality of the mass of both monomorph and the bimorph cantilever beams at the free end of the piezoelectric beams, the power generation capacity of the piezoelectric beams could be significantly increased.