Abstract: Polysaccharides was used as soft template to prepare polysaccharide/Nano-Selenium complexes, which had high biological activity and low toxicity.The preparation procedure of Nano-Se/Cordyceps militaris stroma polysaccharides complexes was investigated by single-factor experiment and orthogonal experimental design, and the water-soluble polysaccharide which was exacted from the abandoned cordyceps militaris culture medium was used as the raw material. The results showed that the optimal reaction conditionswere as follows: the polysaccharide concentration was 10 mg/m L, selenite concentration was 0.4 mol/L, the mixing time was 4 hours, the preparation conditions of dropping was 1.5 r/min. Under the optimal condiction, the ideal morphology, ideal particle size, stable and good nano selenium/Cordyceps militaris stroma polysaccharide complex particles ( CMSP-Se NPs) could be successfully prepared.The antitumor experiment results showed that CMSP-Se NPs could inhibit the proliferation of Caco-2 cells, which presented a certain dose-response relationship.