Spaceborne gamma-ray telescopes are operated within a dominant background of charged particles, mainly primary cosmic rays and Earth albedo particles. Dedicated anti-coincidence devices and on-board rejection techniques are needed to reject this background, as well as the best available background models. The high-energy particle detector (HEPD) is a space detector for high-energy particles, which can identify electrons, protons and light nuclei in the energy range from few MeV to many hundreds of MeV, and measure their fluxes. It consists of a high-precision silicon tracker, a versatile trigger system, a range calorimeter, and an anti-coincidence system. HEPD will extend PAMELA and the AMS-02 measurements to lower energies and characterize the orbital radiation environment, then providing very useful data for the future gamma-ray mission development, especially for the optimization of the on-board background rejection.