An ultrathin palladium film on a porous TiO2 ceramic membrane was successfully synthesized by a novel photocatalytic deposition (PCD) method. The mechanism was interpreted by the photocatalytic reaction between the surface of the TiO2 semiconductor and the Pd(II) solution. Energy dispersive (EDS) analysis and argon permeability of the membrane were used to characterize the deposited Pd. During the PCD process, photoreaction took place with higher efficiency when the pH value of the solution was controlled at the 3-3.5 range. A short irradiation time of 18 min was enough for PCD at a normal reaction temperature. A methanol additive in the solution of about 40 vol % was optimum for the deposition of Pd. XRD and SEM results on the Pd-based membrane prepared by PCD indicated that the metal existed in the form of a pure palladium element, with a layer thickness of about 0.1 mu m. The gas permeation experiment was conducted in a high-temperature permeator from 623 to 723 K. The results indicated that there were contributions to the hydrogen flux attributable to both dense and microholes parts of the resulting Pd/TiO2 membrane.