The present invention relates to a nano-sized photocatalytic sol and application thereof. The invention utilizes spherical nano-photocatalyst and non-spherical photocatalytic sol for coating a photocatalyst layer on a substrate. Because of the stereo, interlaced and composite structure between spherical photocatalyst and non-spherical photocatalyst, a hard and well adhesion coated layer of photocatalyst with good photocatalytic activity can be obtained without using binder.