Abstract: Atheoretical ionospheric model is developed in order to study the variation of ionospheric density profile during geomagnetic storms, considering the disturbances of thermospheric temperature, composition, wind and electric field. The results show that the increase of N₂/O is the most efficient way to decrease the electron density as well as the peak density N_mF₂, but the up and down movement of peak height (h_mF₂) is mainly caused by neutral wind or electric field disturbance. The temperature change has little effect on the profile variation. It is possible to distinguish these different physical processes using f₀F₂ and h_mmF₂ parameters in practical measurement.