The geometry, electronic structure and optical properties of pure rutile-phase TiO2 and HfxTi1-xO2 formed by substituting Hf for Ti in TiO2 were studied by using the plane-wave ultra-soft pseudo-potential method based on the density functional theory. The calculations show that all the compounds of HfxTi1-xO2 are indirect band gap semiconductors. The values of band gap for HfxTi1-xO2 are bigger than that for pure TiO2. The static dielectric constant of HfxTi1-xO2 is smaller than that of pure TiO2 but larger than that of silicon dioxide. The results suggest that HfxTi1-xO2 can meet the requirement on high k materials in microelectronics industry.