O

2

has a significant influence on SF

6

decomposition products under the arc discharge of SF

6

gas insulated switchgear

but its influence and related action mechanism are unclear for now. To this problem

the arc discharge experiments using

18

O

2

as a tracer is performed in this paper

the variation of

18

O isotopic substances during and after discharge by GC-MS is analyzed

the generation path of SF

6

decomposition products under arc discharge and the influence of

18

O

2

on SF

6

decomposition products are defined as well as its deep chemical reaction mechanism is clarified. The results show that under arc discharge

O

2

impurities will promote generation of SOF

2

SO

2

SO

2

F

2

and CO

2

to varying degrees

in which O

2

mainly participates in the generation reactions of SOF

2

SO

2

and CO

2

in the form of decomposed O atoms

and participates in the generation reactions of SO

2

F

2

in the form of both O

2

molecules and decomposed O atoms. The generation of SOF

2

and SO

2

F

2

is mainly dominated by the composite reactions during the discharge

while the generation of SO

2

is mainly dominated by the intermolecular reactions after the discharge. And the generation of CO

2

comes from the combination of the two aspects.