Abstract: VFTO(Very fast transient overoltage) with high amplitude and steep front is produced when disconnector is switched on and off. It is possible to break down GIS internal insulation basin and the secondary side transformer and other adjacent equipment, so it is extremely important to suppress VFTO. Existing scholars have found that ferrite magnetic ring has the characteristics of good suppression effect, easy processing and installation, but the effect of magnetic ring installation position on suppression is not analyzed. Therefore, ATP-EMTP simulation is used to analyze the three most serious points of VFTO for a 1 000 kV GIS: the circuit breaker, the end of BUS5 and the left end of BUS1, and then the effect of different locations of ferrite magnetic ring on inhibiting VFTO is analyzed. It provides reference for further application of ferrite magnetic ring in engineering practice.