Abstract: By numerical simulations the characteristics of the mechanism of equatorial andmid-latitude Spread-F and relations between them are studied. It is found that indifferent latitudes, the same mechanism can evolve into quite different structuresas the background ionosphere is different. Then a theory to explain the discordof disturbance phases in bottomside and topside ionosphere, because it is believedthat through some combinations of ionospheric parameters, bubbles can generatein topside first without much disturbance of the bottomside ionosphere. And bynumerical simulation. A model of radio-wave scattering is put forward to explainthe higher occurrence rate of the blur of radio waves in mid-latitudes than what isexpected by linear theory.