Electron transport types and photovoltage gas-sensitive characters of nano-La1-xSrxFeO3 were probed by the vacuum adsorptive surface photovoltage technique. The results show that the band distortion and the increased anion vacancy caused by doping with a little Sr2+ ions in the nanomaterial are of advantage to form new exciton levels and the localized photogenic free charge carriers, to promote the separation of exciton pairs with increasing sensor gas pressure, and to increase quantum-optical efficiency as result of the effect of surface and quantum confinement.