Use of medicinal chemistry, tissue cells mutate, intermediate acidic metabolites increase the burden on the liver and kidney, chitosan oligosaccharide can and many kinds of harmful substances to form complexes, favorable excretion, detoxification. Radiotherapy is the use of ionizing radiation directly and indirectly killing effect, ultimately killing tumor cells, killing normal cells, coupled with humoral ionization to produce super large amounts of free radicals and to the body to bring great harm. Oligochitosan can effectively remove free radicals, accelerate the excretion, reducing the time in vivo, repair damaged cells. Thus chitosan oligosaccharide to reduce the toxicity of chemotherapy effect is very obvious.