The sensitivity and selectivity of bilayer membrane structure gas sensor prepared by thick film printing technology is studied. The measurement results show that the sensitivity and selectivity of ethanol

acetone

formaldehyde

toluene and other reducing gases can be improved by adding another layer of nano material thick film under the SnO

2

monolayer film. When the concentration is 900 × 10

-6

SnO

2

monolayer of ethanol and acetone sensitivity are 28.1 and 24.7

the sensitivity of WO

3

for ethanol and acetone are 8.9 and 11.3

When the SnO

2

is covered on the WO

3

to form a double layer film

the corresponding sensitivity is improved t

o 43.5 and 52.1.Therefore

the double layer thick film structure provides a feasible method to improve the sensitivity and selectivity. It is believed that the action of the bilayer membrane has a great relationship with the order of the top and bottom alignment of the membrane

and it is also related to the transition layer formed by the diffusion effect.