Lower Yangtze area is an important region bearing hydrocarbon resources of China. Research on the distributions of geotemperature and terrestrial heat flow density possesses considerable significance in the evaluation of hydrocarbon resources and also in the description of thermal evolution of the lithosphere in this area. In this paper, the authors collect all continuous temperature measurements at more than 50 boreholes and select the temperature measurements which may present the formation temperature to determine gradients of geotemperature. Heat conductivities of over 110 core samples Mesozoic-Cenozoic sandstone or mudstone and over 100 outcrop samples of Palaeozoic carbonate or sandstone are measured. Based on these data, values of terrestrial heat flow density are determined at 41 boreholes in this area. The distributions of geotemperature gradients and heat flow densities show that Northern Jiangsu basin and Tanlu fault belt with extension and basaltic eruption in Cenozoic are characterized by high heat flow densities and high geotemperature gradients, and that no obvious thermal anomalies exists in the areas where tectonothermal processes occurred dominantly in Mesozoic.