The present invention relates to a titanium dioxide catalyst supported on a polymer film or membrane substrate, comprising a polymer film or membrane substrate, a titanium dioxide catalyst layer and at least one underlayer in between the polymer film or membrane substrate and the titanium dioxide catalyst layer, characterized in that the at least one underlayer is prepared by means of atom transfer radical polymerization via a reaction between an aminosilane compound and a transition metal compound. The invention also provides a method for preparing the titanium dioxide catalyst supported on a polymer film or membrane substrate comprising the following steps: (1) preparing a solution of atom transfer radical polymerization by reacting an aminosilane compound with a transition metal compound in the presence of an inert gas at room temperature； (2) spraying the solution obtained in step (1) onto the surface of a polymer film or membrane substrate； (3) immersing the sprayed substrate in an organic or inorganic acid solution to introduce reactive hydroxyl functional groups on the surface of the sprayed substrate； and (4) immersing the substrate obtained in step (3) in a solution of titanium dioxide in alcohol, which is adjusted to a basic condition using a basic solution and ultrasonic generator.La présente invention concerne un catalyseur de dioxyde de titane supporté sur un substrat à membrane ou film polymère, comprenant un substrat à membrane ou film polymère, une couche de catalyseur de dioxyde de titane et au moins une sous-couche entre le substrat à membrane ou film polymère et la couche de catalyseur de dioxyde de titane, caractérisé en ce que ladite ou lesdites sous-couches sont préparées au moyen d'une polymérisation radicale par transfert d'atome par le biais d'une réaction entre un composé d'aminosilane et un composé de métal de transition. L'invention concerne également un procédé de préparation du catalyseur de dioxyde de titane supporté sur un substrat à
