In recent years

fluorocarbon environment-friendly insulating gas as a potential alternative to SF

6

gas un-der certain conditions has been widely concerned

in which CF

4

C

2

F

6

and COF

2

are the three main decompositionproducts of carbon-fluorine insulating gas.In this paper

the adsorption ch

aracteristics of above three types of gaseson Ti doped MoS

2

are discussed based on the first-principle.The adsorption energy

charge transfer and state densityof different gas molecules are calculated and compared in case of absorption of different molecule of gases.It isshown by the result that Ti-MoS

2

has a strong adsorption on COF

2

is insensitive to CF

4

and C

2

F

6

and its interactionforce is mainly Van der Waals force.After the adsorption of COF

2

the conductivity of Ti-MoS

2

will increase

while

the conductivity of Ti-Mo S

2

will decrease after the adsorption of CF

4

and C

2

F

6

.Therefore

Ti-doped MoS

2

can selec-tively detect three kinds of gases

which may be used as a new type of resistance gas sensor in the field of on-linemonitoring of gas insulated equipment.