The invention discloses a composition containing catalase and an application thereof. The composition comprises radionuclide, soluble alginate and catalase labeled on a biological macromolecule. The composition can be injected into a tumor by means of interventional therapy. When alginate ions in the composition enter the tumor to encounter calcium ions, a gel is formed, so that radionuclide and catalase are uniformly defined in the tumor. According to the composition containing catalase disclosed by the invention, the anoxic state of the tumor cell is improved by decomposing dissolved oxygen generated by hydrogen peroxide in the tumor by means of catalase, and meanwhile, the tumor cells after anoxic improvement are killed by means of radioactive rays, so that the composition has a good tumor treating application prospect.