In this paper, titanium dioxide/tungsten trioxide nanoparticles were synthesized by sol-gel method. Obtained nanoparticles at different calcination temperatures were analyzed and characterized by X-ray Diffraction (XRD), scanning electron microscope (SEM) and Ultraviolet visible spectroscopy (UV-vis) techniques. The effect of calcination temperature and mole percent on the refractive index (𝑛), extinction coefficient (𝑘) and Abbe number (𝑣𝑑) has been studied. It is shown that at the characteristic wavelength of 500 nm, the refractive index of TiO2/WO3 nanoparticles at calcination temperature of 900oC compared to the calcination temperature of 800 and 700oC at the rate of 3% and 12% increases, respectively. Also, with the increase of 7.5 to 10 mol % TiO2, refractive index has increased dramatically. As well as, with the increase of calcination temperature and mole percent of TiO2, Abbe number increases. This increase of 800 to 900oC and 7.5 to 10 mol % TiO2 is remarkable. Therefore, TiO2/WO3 nanoparticles with 10 mol % TiO2 and 900oC are a suitable option for materials with high refractive index.