Purpose: A charged particle detector (CPD) is one of two main detectors on the GECAM satellite. It was designed to detect charged particles. Electrons and protons are space’s mainly charged particles. So, a research on the proton detection ability of a CPD and deriving the energy response to charged particles of the CPD in the two designed operating modes is important.Method: The proton calibration tests of the CPD under different working modes were carried out at the Heavy Ion Research Facility in Lanzhou.Result and conclusion: Through testing and analysis, it was concluded that when CPD works in semi-component mode, it can detect the maximum energy, and when working in full-component mode, it can provide better energy resolution.