The invention relates to a carbon dioxide thermochemical cyclic decomposition system and aims to provide a method for preparing carbon monoxide from carbon dioxide by photothermal chemical cyclic decomposition. The method comprises the following steps: mixing zinc nitrate, deionized water, glacial acetic acid and anhydrous ethanol to obtain a solution A, adding tetrabutyl titanate into anhydrous ethanol to obtain a solution B, pouring the solution A into the solution B, stirring into a gel, drying the colloid, grinding into fine powder, and roasting by heating to obtain binary composite metal oxides; and after irradiating with a light source to react, introducing CO2, and heating to react to generate CO. By combining photochemistry and thermochemistry, since the titanium-zinc binary composite metal oxides are irradiated at normal temperature under normal pressure to be decomposed into metal suboxide and oxygen, the temperature required by the first step of the thermochemical cycle is greatly lowered, thereby improving the cyclic conditions.