The invention provides a preparation method of a metal ruthenium nano material. The preparation method comprises the following steps that 1, a metal ruthenium complex is dissolved in a polycarboxyliccompound aqueous solution, and ultrasonic dispersion is carried out to obtain a mixed solution A, wherein the metal ruthenium complex is formed by coordination of a polypyridine ligand containing amino and ruthenium trichloride; 2, water bath heating is carried out on the mixed solution A to obtain a reaction solution B; 3, the pH value of the reaction solution B is adjusted by using an alkaline reagent, then supernate of the reaction solution B is dialyzed, an aqueous solution obtained through dialysis is collected and freeze-dried, and the metal ruthenium nano material is obtained. Accordingto the preparation method of the metal ruthenium nano material, protonation of amino and a hydrothermal method are used, the metal ruthenium complex difficult to dissolve in water is wrapped with thewater-soluble polycarboxylic compound, so that the prepared metal ruthenium nano material is good in water solubility, high in light stability, relatively high in fluorescence quantum yield, high intumor photodynamic therapy, good in biocompatibility and high in singlet oxygen yield.