The stability of LaFeO

3

-V

2

O

5

composite to SO

2

is systematically studied

and its sensitive mechanism is analyzed.The research shows that when the ratio of LaFeO

3

and V

2

O

5

is 1∶1

the average response to 50×10

-6

SO

2

at 500 ℃ is 116.32 %

and the drift rate of air resistance during continuous testing is only 1.17 %.The reason is that after the two are combined

SO

2

originally adsorbed on LaFeO

3

overflow to the surface of V

2

O

5

and cataly

ze the conversion into gaseous SO

3

for desorption because of the overflow effect.