In this work, gas response properties of Pd modified TiO 2 sensing films are discussed when exposed to H 2 and O 2 . TiO 2 films are surface modified in PdCl 2 -containing solution by the dipping method and treated for different treatment times to get different surface states. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Kröger–Vink defect theory are used to characterize the sensing films. The gas response properties indicate that the sensor response time which related to the rate of change of sensor resistance is affected by the activation energy (E). In particular, the sensor treated at 900°C for 2h exhibits a response time of about 20–240ms when exposed to H 2 and 40–130ms when exposed to O 2 at 500–800°C.