This invention discloses a photosensitive phosphorylated phenol-formaldehyde resin, characterized by containing in its molecule at least two phosphate groups, each phosphate group coupled with at least one photo-sensitive group. The photosensitive resin of the present invention is prepared by reacting a phenol-formaldehyde resin with phosphorus oxychloride to form a phosphorylated phenol-formaldehyde resin; then reacting the resin with a compound having one hydroxyl group and at least one ethylenically unsaturated bond, thereby esterifying some of the phosphorochloridate groups to produce a resin having ethylenically unsaturated bonds and unreacted phosphorochloridate groups; and hydrolyzing the unreacted phosphorochloridate groups into phosphoric groups. The photosensitive resin according to the invention is UV-curable and alkaline-soluble as traditional photosensitive resins are; moreover, it exhibits good flame retardant and adhesive properties.