C/2019 Y4 (ATLAS) is an Oort cloud comet with an orbital period of ∼5895 yr. Starting in 2020 March, its nucleus underwent disintegration. In order to investigate the gas and dust properties of C/2019 Y4 (ATLAS) during its disintegration, we obtained long-slit spectra at 3600–8700 Å and BVRI multiband images with the Xinglong 2.16 m Telescope in 2020 April. Our observations revealed that C/2019 Y4 (ATLAS) exhibited strong emission bands of CN, C2, C3, and NH2, which are superimposed on a dust-scattering continuum, typical of cometary spectra in the optical. The production rates of CN, C2, and C3 derived using the Haser model and the corresponding C2/CN and C3/CN ratios suggest that C/2019 Y4 (ATLAS) is a “typical” Oort cloud comet under the A’Hearn classification, although it appears less dusty, as revealed by the Af ρ quantities. Its dust-scattering reflectivity is slightly red, with a gradient of ∼5% per 103Å. We model the reflectivity gradient in terms of porous dust and find that the red color is accounted for by porous dust.