The study on the decomposition characteristic of C

4

F

7

N/CO

2

can provide important technical reference forthe fault diagnosis of C

4

F

7

N/

CO

2

power equipment.The overheating experimental platform is set up to simulate theearly local overheating fault of C

4

F

7

N/CO

2

power equipment and the infrared detection platform is set up by FTIRtechnology.In order to improve the efficiency and accuracy of infrared qualitative analysis of C

4

F

7

N/CO

2

thermal de-composition products

the gas mixture before and after the overheating experiment is detected by fourier transforminfrared spectroscopy and gas chromatography-mass spectrometry.It is found by the study that the at the experimen-tal condition that C

4

F

7

N/CO

2

gas mixture containing about 300μL/L C

4

F

7

N at intensity of pressure at 0.100 MPa

thetemperature of 500℃and the heating time of 10 h has such thermal decomposition product as CO and C

3

F

6

whichis detected by FTIR.The infrared absorption of CO is concentrated in the 2 000～2 220 cm

-1

band;There is a singleinfrared absorption peak of C

3

F

6

in the 1 000～1 100 cm

-1

band

1 780～1 820 cm

-1

band

and two adjacent infraredabsorption peaks exist in the 1 180～1 250 cm

-1

band

1 300～1 450 cm

-1

band.The related study result can provideimportant reference for fault diagnosis of C

4

F

7

N/CO

2

power equipment.