Detailed simulations of buffer gas cooling, which is widely applied at the rare-isotope facilities, have been investigated by using three frequently used models: viscous damping force (VDF) model, hard sphere collision (HSC) model, and realistic interaction potential (RIP) model. By comparing the stopping ranges from the simulated data with those from SRIM code, we found that the VDF and HSC models are better in low energy range, but the RIP model is better in relatively high energy range. In helium buffer gas, which is always used in cooler and bunchers, the VDF model should be used when the ion’s energy is less than ∼5 eV/u, and the RIP model less than

∼80 eV/u. Above this energy, all three models cannot be

used.