A new crystal, Ca₂(Al_1.8Ga_0.2)SiO₇, was obtained by substituting Ga³⁺ ions for some Al³⁺ ions in Ca₂Al₂SiO₇ crystal. The growth, structure and optical spectroscopic properties of Cr⁴⁺-doped Ca₂(Al_1.8Ga_0.2)SiO₇ were studied. It shows strong absorption at 693 and 762 nm and a broad emission band with peak wavelength at 1223 nm. Both the absorption and emission peaks of Cr⁴⁺-doped Ca₂(Al_1.8Ga_0.2)SiO₇ crystal are red-shifted in comparison with that of Cr⁴⁺-doped Ca₂Al₂SiO₇ crystal due to its weaker lattice field. The investigation results show that there is only one kind of tetrahedral site for Cr⁴⁺ occupation in the lattice of Ca₂(Al_1.8Ga_0.2)SiO₇ crystal.