Xu Guangxian is a leading scientist in rare earth chemistry and separation technology. He established a new theory of countercurrent extraction in 1970s, which is applicable for separation of a mixture with more than ten components such as rare earths. Based on his theory, he built up a new extraction separation flow sheet, which has been extensively used in the major rare earth separation factories in China with great success. In this paper, Xu Guangxian described his research experience on rare earth and their separation technology. The method for science and innovation and patent protection were discussed.