A two-degree-of-freedom cantilever beam piezoelectric generator was explored to improve the generation performance of the cantilever beam piezoelectric generator under the variety of the ambient vibration energy sources. The theoretical model of the frequency characteristics of the two-degree-of-freedom cantilever beam piezoelectric generator was established and finite element analysis was performed for the proposed theoretical model. The theoretical results show that the theoretical analysis and finite element simulation are in agreement well. A numerical simulation was carried out for the frequency characteristic model of the two-degree-of-freedom cantilever beam piezoelectric generator and the results show that the ratio of the 1st modal frequency to the 2nd modal frequency will be a minimum value with the increase of the length ratio, width ratio, thickness ratio and the mass ratio, and the minimum value of the ratio of the 1st modal frequency to the 2nd modal frequency can be obtained at the length ratio of 0.8, width ratio of 2.0, thickness ratio of 1.0, and the mass ratio of 0.5. The results demonstrate that the frequency-band of the two-degree-of-freedom cantilever beam piezoelectric generator is expanded by optimizing the structure parameters to reduce the distance between the 1st modal frequency and the 2nd modal frequency. Finally, the two-degree-of-freedom cantilever beam piezoelectric generator was designed and the broadband generation performance of the generator verified.