Abstract: A method for making a beam splitter with photocatalytic coating is disclosed. First, a TiO2—SiO2 sol, a SiO2 sol, and an anatase TiO2 preform sol are prepared. A glass substrate having two opposite surfaces is provided. The two opposite surfaces of the glass substrate is coated with the TiO2—SiO2 sol, the SiO2 sol, and the anatase TiO2 preform sol by dip-coating, thereby forming a coated glass substrate with a multi-layer optical coating on each of the two opposite surfaces. The multi-layer optical coating comprises a TiO2—SiO2 coating, a SiO2 coating, and an anatase TiO2 preform coating. The coated glass substrate is subjected to an anneal process. The coated glass substrate is cut, thereby forming the beam splitter with photocatalytic coating.