The data from the International GPS（global positioning system） Service（IGS） are used to investigate the characteristics of the sudden increase of the ionospheric total electron content(Q

TEC

) response to the solar flare.Based on the methods of differential time delay and differential phase advance

research on the solar flare occurring on Oct.28

2003 indicated that the largest increase of the Q

TEC

is（17.7） TECU(1 TECU=10

16

e·m

-2

).When local solar zenith angle is larger than 40°

the increase of Q

TEC

has inversely-proportional relationship to the solar zenith angle.The

inversely proportional coefficient can be got by fitting.Compared with the solar flares on Oct.29

2003 and Nov.4

2003

the relationship between the inversely-proportional coefficient and the increase of Q

TEC

caused by the solar flares can be determined.Analyzing the spacial variation of Q

TEC

as a result

the spacial variation could be ignored while studying the Q

TEC

temporal variation response to the solar flare.