A new quaternary noncentrosymmetric sulfide Y4GaSbS9 has been synthesized by high-temperature solid-state reaction. Title compound adopted a known RE4GaSbS9-structure type in the orthorhombic space group Aba2 (no. 41). The large optical gap of 2.06 eV for Y4GaSbS9 was deduced from UV/Vis reflectance spectroscopy. DFT calculations are used to study the electronic structure and nonlinear optical properties of Y4GaSbS9.