Three isolated substorms occurred during Apirl 28-29

2001.Data of International GPS（Global Positioning System） Service network is used to study the morphology of ionosphere response to these substorms.In comparison of the characteristics of QTEC deviations to its quiet time values in different latitudes and longitudes and correlation analysis of AE index to ΔQVTEC in Europe-Africa sector

we can obtain results as following: isolated substorm can arose globally large scale ionosphere disturbances with amplitude up to more than 20TECU（1TECU=1016e·m-2）.The disturbance status is strongly dependent on local time

as well as latitudes.Without interferences between different responses

the occurrence of isolated substorm has strongly linear correlation with that of ionosphere disturbances.The negative correlation response appeared in high latitudes while positive correlation appeared in middle/low latitudes.