Abstract:Based on the Tropical Cyclone (TC) Yearbook's data of JMA from 1979 to 2007, statistical analyses were performed to study the extratropical transition (ET) of tropical cyclones over mainland of China. Results indicated that there were 16 tropical cyclones over the mainland of China, which accounted for 8.56% of the total number of tropical cyclones that made landfall on China during the 29 a, only 8 of these ET cases got strengthened after transition. In addition, the moist potential vorticity (MPV) and the dynamic, thermodynamic processes analyses of the 8 ET cases're-intensification revealed that the combination of the dynamic and thermodynamic processes was able to define a development region in which it was favorable for intensification of most ET cases over mainland of China during the 29 a. Moreover, the upper-level positive MPV propagated downward to lowlevel during the obvious reintensification phase of ET, however, the upperlevel positive MPV did not always propagate downward when the ET of TC was reinforced only a little.