TiO2 thin films on GaAs(1 0 0) substrates were prepared at temperature ranging 30-750 degreesC and pressure from 5 x 10(-4) Pa base vacuum to 15 Pa O-2. by pulsed laser deposition (PLD). The effects of both the oxygen pressure and the substrate temperature on the properties of TiO2 films were investigated. TiO2 thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). Optimum parameters have been identified for the growth of high-quality TiO2 films. At 5 Pa of oxygen ambient pressure. rutile TiO2 films with high [1 1 0] orientation were formed at substrate temperature of 700 degreesC. At room temperature (30 degreesC) and 5 x 10(-4)Pa base vacuum, rutile TiO2 films with a preferred [1 1 0] orientation were also obtained on GaAs(1 0 0) substrates by PLD. Surface morphology of the films showed marked dependence on the substrate temperature, The grain size and their surface roughness increased with raising substrate temperature.