This paper presents the real-time observation of the Bragg grating formation in As2S3 channel waveguides. Channel waveguides (width~10μm) are obtained by a photolithographic process applied to a thin layer (~0.6μm) of thermally evaporated As2S3. The photoinduced variation of the refractive index is the principal mechanism involved in the formation of the Bragg grating. We used a typical holographic setup, with an Argon ion laser as recording source, to photoinduce gratings with Bragg wavelength ranging in telecommunication window. The time evolution of the transmission spectrum during illumination is also presented and analyzed here.