Abstract: The characteristics and development of the ionospheric storm between Nov. 6 and Nov. 12, 2004 was studied using the total electron content （TEC） derived from GPS data observed by globally-distributed GPS stations under International GPS Service for Geodynamics （IGS）. It was found that when magnetic storm was in its main phase on Nov. 8, the ionospheric positive storm occurred over a large region of mid-and low latitude in the day time. And during the recovery phase on Nov. 10, when Dst index reached its minimum, the global ionosphere was intensely disturbed and both positive and negative effects appeared. During this storm, negative effects appeared more intensely in the southern hemisphere （the summer hemisphere） than in the northern one, which is consistent with previous statistic results that negative storms have a proneness to appear in the summer hemisphere. It has been also observed that during the storm the value of night time TEC is low comparing the night TEC with no storm period, for which many mechanisms has been proposed. Because of the complex evolution process of ionospheric storm, more data including from other observation methods during other large ionospheric storms needs to be collected and analyzed.