NOVELTY - Preparation of photocatalyst coating composition involves hydrolyzing titanium compound using water, adding ethanol and acid to perform hydrothermal synthesis reaction to obtain first titanium dioxide photocatalyst sol; adding acid to perform hydrolysis synthesis reaction to obtain second titanium dioxide photocatalyst sol; mixing the two photocatalyst sol; hydrolyzing or adding acid after hydrolyzing; and mixing the titanium dioxide photocatalyst sol mixture, the colloid silica sol and ethanol.    USE - Method for preparing photocatalyst coating composition useful in glass substrate for solar battery module (claimed).    ADVANTAGE - The glass substrate for solar battery module having the compound oxide coat made of photocatalyst coating composition has good durability and weatherability, high transmittance, low reflectivity, and increases maximum output quantity of the solar battery module.    DETAILED DESCRIPTION - Preparation of photocatalyst coating composition involves:    (A) hydrolyzing titanium compound using water, adding ethanol and acid to perform hydrothermal synthesis reaction to generate titanium dioxide crystal to prepare first titanium dioxide photocatalyst sol;    (B) heating, and adding acid to perform hydrolysis synthesis reaction to prepare second titanium dioxide photocatalyst sol;    (C) mixing the two titanium dioxide photocatalyst sol to prepare the titanium dioxide photocatalyst sol mixture;    (D) using excessive water to hydrolyze the silicate compound under the acid condition, or adding the acid after hydrolyzing to prepare the colloid silica sol; and    (E) mixing the titanium dioxide photocatalyst sol mixture, the colloid silica sol and ethanol.    INDEPENDENT CLAIMS are included for:    (1) photocatalyst coating composition comprising titanium dioxide (0.5-5 wt.%), silicon (0.5-3 wt.%), water, and alcohol;    (2) glass substrate for solar battery module comprising a surface containing compound oxide coat formed by hot set after coating the photocatalyst coating composition on the surface of the glass substrate; and    (3) solar battery module comprising the glass substrate as the front substrate.