Due to the advanced performances of multi-stable systems, multi-stable energy harvesters have been extensively concerned and rapidly developed in the past few decades. The attractive characteristics of a multi-stable system are their intricate snap-through motions when ambient vibrations are introduced. Many experiments on the energy harvesting performances of multi-stable energy harvesters have demonstrated that multi-stable energy harvesters have high-efficiency energy harvesting characteristics in comparison with their counterparts of monostable energy harvesters. The energy harvesting performances of multi-stable energy harvesters remarkably depend on the form of system potential energy. Therefore, optimal design of potential function is of great significance for improving the performance of multi-stable energy harvesters. This paper presents a theoretical perspective for modeling piecewise multi-stable potential functions and investigating the dynamic characteristics of the designed multi-stable energy harvesters. Bifurcation analysis and Poincaré mapping are employed to understand the nonlinear mechanisms of cross-well and in-well motions. Furthermore, the broadband energy harvesting capacity of parametric multi-stable energy harvesters is estimated and discussed.