A new class of particle simulation models has been developed which eliminates the high‐frequency space charge oscillations while keeping the low‐frequency ion‐density fluctuations unmodified. Physically, the quasi‐neutrality is maintained as the adiabatic electrons follow the ion‐density fluctuations so as to establish the Debye shielding. It is, therefore, possible to use an integration time step comparable to the characteristic time scale of the low‐frequency oscillations so that realistic plasma parameters can be used in the present simulation model. Applications to ion sound wave propagation, ion‐ion two‐stream instability, and the low‐frequency fluctuation spectrum in a magnetic field are given. The way in which to include the nonadiabatic electrons in the model is also discussed.