Human health every day will produce more than 1 million cancer cells and chitosan oligosaccharide is with basic groups of the polysaccharide, can make the blood pH to alkaline shift, resulting in the activation of lymphocytes, put it in a state of optimal activity, improve the function of LAK cells 3 times the left and right sides, NK cell activity increased by about 4.5 times, these immune cells are a key factor in anti-cancer. In addition, cancer cells produce quantitative mutation is a prerequisite for body fluids acidic, and chitosan oligosaccharide just can improvement and prevention of body fluids acidic, body fluids can keep cancer cells to survive environmental conditions of differentiation, fundamentally to the occurrence of cancer prevention.