A new theoretical model for SrTiO3 physisorption and chemisorption has been developed to quantitatively analyze the effect of relative humidity on electrical conductivity of the amorphous porous SrTiO3 film.This model may also be applied to other type of porous semiconductor ceramics.In this paper,the SrTiO3 film is deposited on SiO2/Si substrate by using the argon-ion beam plating technique,and then formed a planar resistor structure on SrTiO3 film. The experimental results show that, at room temperature,the current decreases slowly when relative humidity changes from 12% to 53%, and then increases rapidly with the increase of relative humidity from 53% to 92%.The current and its rate of change increase with increasing test frequency.The response time of water adsorption is longer than desorption.