A composition comprising catalase, a preparation method and a use thereof, and a method for killing tumor cells are provided. The composition comprises a radionuclide labeled to a biomacromolecule, a soluble alginate and catalase. The composition can be injected into the tumor through an interventional treatment. A gel is formed when an alginate ion in the composition enters the tumor and encounters a calcium ion, such that the radionuclide and the catalase are uniformly confined in the tumor. The composition comprising catalase utilizes catalase to decompose dissolved oxygen generated from hydrogen peroxide in the tumor to advance the hypoxic state of the tumor cells, and the tumor cells are killed with radiation after the hypoxic state thereof has been advanced, and thus the invention has good prospects for applications in cancer therapy.
