Abstract: Optical properties in a novel two-dimensional carbon material (single layer net-Y) are investigated by using first-principles calculations based on density functional theory. A detailed analysis of the behavior of optical properties is given based on the reflection, absorption, refractive, dielectric functions, and so on. The results reveal that the complex dielectric function, the complex refractive function, the absorption coefficient et al. of the single layer net-Y exhibit significant anisotropy under E_x, E_y and E_z polarizations. The optical properties show that the material has very insensitive light reflection properties in the whole light region, and it has a high absorption coefficient and a very low extinction coefficient at about 10.0 eV in the ultraviolet region. In addition, compared to the light with other wavelengths, single layer net-Y presents a stronger optical refraction response to yellow light under the E_y polarization.