Abstract: To determine the uranium contents and discuss the degree of uranium polution in Er-Sea and Nanming River on Yannan-Guirhou Pltaeau,two kinds of water samples collected from the part with different degree of contamination in Er-Sea and Nanming River are radiated by slow neutron in a nuclear reactor.The tracks of uranium decay fragements in the water samples are produced in SSNTU and etched by NaOH.The number of fission tracks is counted under a microscope.the result shows that the uranium content in Nanming River is more greater than Er-Sea.The situation of uranium polution in Nanming River and other rivre at home and foreign is also discussed in light of comparison among them.