The experimental procedure of the Uranium Series Disequilibrium TIMS Method for dati ng volcanic rocks was set up for the first time in China, and the ages of samp les from the Ten gchong volcanic field, Yunnan Province, and Changbaishan Tianchi volcano, Jilin P rovince, were obtained. Based on this ages, the cycles of volcanic eruption can b e inferred as follows: 220 ka, 80 ka, 20 ka, 12.8~13 ka, 0.75~0.79 ka for the Ten gchong vo lcanoes since the late Pleistocene and 5.3 ka, 1.0 ka, 0.75 ka for the Tianchi v olcano sinc e the Holocene. All these ages are almost same as those given by variable other met hods indicating that they are reliable. In addition, the principle and some prob lems such as closed system of the samples and homogeneity of Th isotope composit ion in magma are discussed.