In this paper, a TiO₂ film/tin-diffused glass composite optical waveguide (OWG) component is prepared by the dip-coating method, and a zinc phthalocyanine (ZnPc) sensitive layer is fixed on the surface by the spin coating method to prepare a highly-sensitive hydrogen sulfide (H₂S) gas sensor based on a composite OWG. The preparation conditions of sensors is optimized. When the dip-coating speed of the dip coater is 80 mm·min ^-1, the rotating speed of the spin coater is 1600 r·min ^-1, and the mass fraction of the ZnPc solution is 0.05%, the sensor has the best selective response to H₂S gas and can detect the H₂S gas with a volume fraction of 1×10 ^-9. In addition, the sensor shows good stability within one month.