Abstract: A series LaxBa_1-xTiO₃ nanocrystals were preparaed by Sol-Gel method under various processing conditions. The alcoxide was used as starting material and glacial acid, non-alchol agent, acted as homogeneous catalyst. Then the ceramic humidity sensor was formed through the cold-pressing, sintering and capsulating. At room temperature, its electric resistance was measured by RLC impedimeter D.C.bridge. And RQ-1 Gas meter was employed to determine the sensibility of alcohol, benze, enthene, hydrogen and so on. The results showed that the sensor ,sintered at 1300 ℃/1 h,doped by 9 mol%La(OEt)₃, had high humidity sensitivity and short respond-time. The relationship between logarithmic resistance and relative humidity was linear. The sensor didn’t respond to the gases referred above. The microstructure was observed by scanning electronic microscopy and the crystalline phase and its grain size was determined by XRD.