The invention provides a cordyceps militaris extractive. The weight ratio of cordyceps polysaccharide to cordycepin in the cordyceps militaris extractive is (1-25): 1. The cordyceps militaris extractive is selected from an artificial cultivated cordyceps militaris fruiting body extractive, an extractive obtained from an artificial cultivated cordyceps militaris culture medium and a complex of the extractive obtained from the artificial cultivated cordyceps militaris culture medium and cordyceps militaris fruiting body fine powder. The invention also provides an application of the cordyceps militaris extractive in the preparation of the medicines for treating tumors. The tumors include solid tumors and non-solid tumors such as one or more than one of liver cancer, lung cancer, breast cancer and sarcoma or leukemia. The medicines are capable of enhancing an immune function and reducing the toxicity of radiotherapy medicines or chemotherapy medicines and have therapeutic effects of collaborative radiotherapy or chemotherapy.