The invention discloses a solar spectrum selective absorption coating and a preparation method thereof. The absorption coating comprises a metal infrared high-reflection layer, an absorption layer, an antireflection layer and a protection layer which are successively arranged outwards from a substrate, wherein the absorption layer is formed by transition metal nitrogen oxide MoxAl1-xOyN1-y or WxAl1-xOyN1-y; x is 0.1-0.9; y is 0.1-0.9. The preparation method of the solar spectrum selective absorption coating comprises the following steps: (1) preparing the metal infrared high-reflection layer on the surface of the substrate via a direct-current magnetron sputtering method; (2) carrying out co-sputtering of an Mo or W and Al pure metal target or an MoAl or WAl target with fixed components in the atmosphere of argon, nitrogen and oxygen to form the adsorption layer; (3) selecting an Al target and preparing the antireflection layer via a direct-current or medium-frequency magnetron sputtering method; and (4) selecting an Si target and preparing the protection layer via the direct-current or medium-frequency magnetron sputtering method. The absorption coating has the characteristics of excellent optical performance, strong high temperature resistance and excellent weather resistance; the preparation method of the absorption coating is easy to implement and simple to regulate, and is suitable for the application status of flat plate collectors in China.