Abstract: A physical model for ionospheric vertical profile is established, taking into ac-count four species of ions and electrons in the region of 80-500 km. Neutral windand ions' motion are both involved in the continuity equations for those five species.Ionospheric proflles in different seasons at low and high solar activities are calcu-lated and compared with the results from IRI-90. Results show that E region is atypical Chapman layer and the depth of E-F valley is generally 0.2-0.5 which isdeeper than that given by IRI-90. That the F₁ ledge is most obvious in summerat low solar activity is consistent with widely accepted theories, but the F₁ ledgeseldom appear in IRI-90. In F₂ region, the electron number density at high solaractivity is greater than that at low solar activity, and in winter is greater than thatin summer. rhese all agree with observations rather well.