Abstract The interannual variation,seasonal variation,diurnal variation and spatial distribution characteristics of TEC in China are investigated with time series analysis,spectrum analysis and wavelet decomposition using the global ionospheric grid data provided by IGS from 1999 to 2013.The main features are as the followings:TEC varies greatly in the daytime while slightly in the night with the spatial distribution;overall,the TEC value in the low latitude area is higher than that in the mid latitude.In the winter,TEC value in the low latitude is lower than that in the midlatitude.Within a day,peak value appears during LT 12:0016:00 and valley appears during LT4:006:00.In the periods,the peak time moves forward with the increase of latitude.This rule may provide certain reference to modify K8 model which set peak time as fixed.The spring is quiet period,in which TEC reaches its maximum value of a year,and the autumn is active period.TEC has obvious semiannual period of about 183 days.In addition,the analysis of long time sequence shows that winter anomaly does not exist in China,except in 2001.