Clean version of the Abstract A preparation method for growing a germanium sulfide (GeS2) single-crystal thin film on a SiO2 substrate includes: cleaning a surface of a substrate with acetone, ethanol and deionized water, where the substrate is a Si/SiO2 substrate or a SiO2 glass substrate; photoetching the substrate, spin-coating a photoresist, and performing photoetching and dry etching or wet etching to obtain a groove pattern; depositing a germanium (Ge)-crystal layer in the groove pattern of the substrate to obtain a treated substrate; and putting the treated substrate into a chemical vapor deposition (CVD) device for growth, a growth source being high-purity sulfur (S) powder and high-purity Ge powder, thereby obtaining a GeS2 single-crystal thin film on the SiO2 substrate. The preparation method can grow GeS2 single crystals on the SiO2 substrate. The GeS2 single crystals have a high crystalline quality and a small surface roughness.