In this work, using large-sized single crystals of high optical quality, the optical properties of Ba₂TiSi₂O₈ were systematically investigated, including transmission spectra, refractive indices and nonlinear absorption properties. The crystal exhibits a high transmittance (>84%) over a wide wavelength range from 340 to 2500 nm. The refractive indices in the range from 0.31256 to 1.01398 μm were measured, and Sellmeier’s equations were fitted by the least squares method. The nonlinear absorption properties were studied by using the open-aperture Z-scan technique, with a nonlinear absorption coefficient measured to be on the order of 0.257 cm/GW at the peak power density of 16.4 GW/cm². Such high transmittance and wide transparency indicate that optical devices using the Ba₂TiSi₂O₈crystal can be applied over a wide wavelength range. Furthermore, the small nonlinear absorption observed in Ba₂TiSi₂O₈ will effectively increase the optical conversion efficiency, decreasing the generation of laser damage of the optical device.