At present

the use of C

4

F

7

N/CO

2

gas mixture as the alternative insulating medium to SF

6

is highly feasible in the power industry

yet its arc-quenching performance remains to be further studied. In this paper

the free arcing dynamic process in rod-rod electrode gaps based on the magneto hydro dynamics (MHD) theory is simulated

and the arc voltage-current characteristics of C

4

F

7

N/CO

2

gas mixture (the percentage of C

4

F

7

N is 7%

10% and 20% respectively

) and SF

6

at 0.6 MPa is calculated. The study results show that the C

4

F

7

N/CO

2

gas mixture exhibit stronger axial diffusion ability than that of SF

6

. Compared to C

4

F

7

N/CO

2

gas mixture

SF

6

has lower arcing temperatures and the increase of the proportion of C

4

F

7

N can reduce the arcing temperature. During the arcing process

the arc voltage of SF

6

gas is the lowest

and the increase of the proportion of C

4

F

7

N can significantly reduce the arc voltage of the gas mixture.