To harvest low-frequency and high-level vibration energy, a piezoelectric vibration energy harvester with serial-connected piezodiscs (PVEH) was presented. The influence of the number and circuit-connection methods of the piezodiscs, lumped mass, and driving frequency on the output performance was studied theoretically and experimentally. The research results show that the increasing of the number of the piezodiscs and lumped mass is helpful to reducing natural frequency and rising energy generation as well as output power of a PVEH. In the case of piezodiscs connected in serial and parallel, the open circuit voltage and the optimal resistance load for the PVEH to obtain maximal power are different, but the generated electric energy and the maximal power at the optimal loads are equal to each other. PVEHs with 1/2/4 pair of piezodiscs were fabricated and tested. For a pair piezodiscs, the optimal frequency and generated energy of the PVEH with lumped mass of 292 g are 0.6 times and 1.92 times those with lumped mass of 36.5 g. As for 4 pairs of pizoediscs connected with parallel circuit, the optimal frequency and generated energy are 0.58 times and 2.2 times those of a single pair of pizoediscs. The optimal loads and the maximal power for 2 pairs of piezodiscs connected in serial/parallel are 42.3/10.6 kΩ and 232.8/202.7 mW, respectively.