Abstract: The first location of the lake sediment deposition is at the lake bottom, so the temperature of the lake bottom not only has influence on the preservation of organic matter, but also has influence on the formation temperature under the lake bottom. The ancient water body temperature, especially the temperature of the lake bottom becomes a key aspect in estimating the exploration prospect. According to the comparison between the previous research result of the paleoclimate and the nowadays climate, the average annual temperature during the Cretaceous period of the Songliao Basin is between 14 ℃ and 24 ℃. Using the reservoir temperature calculation method, and the data on the palaeolatitude and the paleowater depth, the palaeo-temperature of the lake surface of the Songliao Basin is between 17 ℃ and 25 ℃; the temperature of the bottom water is between 6.2 ℃ and 12.5 ℃ in the deep lake; the temperature of the deepest lake bottom is between 4.0 ℃ and 11.3 ℃. During the period of the Qingshankou Group and Nenjiang Group deposition, the temperature of the lake bottom did not change much with the seasons, and the temperature was low (about 8 ℃)，and the stratification was clear. Therefore, the lower temperature at the lake bottom is favor of the Cretaceous biogas exploration in the Songliao Basin.

Key words: Songliao Basin, Cretaceous, palaeo-climate temperature, temperature of lake bottom, biogas