MgO-SBA-15 has been successfully developed as a kind of humidity-sensitive material. The structure of MgO-SBA-15 materials was characterized by XRD, IR spectroscopy, N₂ adsorption–desorption, TEM and XPS. The study proved that the MgO did not destroy the mesoporous structure of SBA-15 via the characteristic results of XRD and N₂ adsorption–desorption. Researchers built the thick film humidity sensors on the Al₂O₃ ceramic substrate with two Ag–Pd interdigital electrodes with five fingers. The sensor shows excellent humidity sensitivity from 11% to 95%RH, and it has very good response and recovery property. The response time is about 10 s and the recovery time is about 20 s. We found that the mesoporous structure of the sensing materials contributed to the humidity sensitivity. We discussed a possible mechanism based on the humidity sensor produced by MgO-SBA-15.