A superhydrophilic thick-film pH sensor based on chemical etching, and a preparation method thereof are provided. The superhydrophilic thick-film pH sensor includes: a substrate, and a working electrode and a reference electrode that cover surfaces of the substrate. The working electrode includes a titanium sheet attached to one side of the substrate; a front part of an outer surface of the titanium sheet is covered with a titanium dioxide sensitive layer; an electrically-conductive layer is attached to the other side of the substrate; the reference electrode is located on the electrically-conductive layer, and a surface of the reference electrode is coated with a naphthol layer; and an insulating gel wraps the substrate to expose only the working electrode and the reference electrode. The working electrode is obtained by soaking the titanium sheet in an 80° C. NaOH solution, and is integrated with the reference electrode to produce the thick-film pH sensor.