Abstract: As an important part in the near-Earth space environment,the ionosphere activityis closely related to human survival and development and has a significant impact for produc-tion and life of human beings.At present,most studies are based on the ionosphere iono-spheric total electron content(TEC).It can only reflect the level of the ionosphere struc-ture,but cannot reflect the vertical structure of the ionosphere.Computerized ionospherictomography(CIT)technology based on GNSS is most convenient and effective.AnalyzingCIT techniques,some conditions are proposed to prove its accuracy and reliability.Using ob-servation data provided by IGS stations on August 3,2010,an ionospheric image of the Eu-ropean region is reconstructed.It shows the feasibility of this method.