Abstract: Southeast China is tectonically characterized by complex geological evolution and intensive Mesozoic-Cenozoic intracontinental deformation. The thermal structure of the continental lithosphere in SE China and its influence on tectonics still remain open. Here we combine the latest heat flow data with the Crust 1.0 model to construct the lithospheric thermal structure for the Yangtze Craton, Cathaysia Block and South China Sea, using the steady-state heat conduction equation, and constrained by independent xenolith and seismological observations. The results show that the thermal structure is of strong heterogeneity in SE China. Most regions are indicative of a ‘hot crust and hot mantle’ thermal structure, except for the Upper Yangtze Region (e.g. Sichuan Basin), where the type of ‘warm crust and warm mantle’ exists. The deep temperatures in the Cathaysia Block and South China Sea are significantly higher than those of the Yangtze Craton at the same depth. The thermal lithosphere thins gradually southeastward from ~200 km in the craton interior to ~110 km in the Cathaysia Block and then to ~70 km in the South China Sea. In addition, the distribution of intracontinental earthquakes is found to be closely related to temperature, i.e. seismicity mainly occurs within the 600 ℃ isotherm. In general, the central-western Yangtze Craton is of cold and thick lithosphere, while the Cathaysia Block and the northern South China Sea is of hot and thin lithosphere, as the results of the Paleo-Pacific plate flat subduction and Cenozoic magmatism in the continental margin. The inherited thermal weakening facilitated the rifting of the SE China continent margin and the subsequent opening of the South China Sea. 

Key words: Thermal structure, lithosphere, continental margin, South China