The invention belongs to the field of buildings and water storage, and particularly relates to an underground concrete impounding reservoir heat preservation method. The method comprises the steps that an algorithm is provided for judging whether or not insulation measures need to be taken to an underground concrete impounding reservoir of a region, a heat preservation material is selected througha calculation result, the specific heat preservation structure is designed, and a heat preservation material is used for performing heat preservation treatment on the top and the walls of the underground concrete impounding reservoir. The method can avoid the problems that the cost of the reservoir is excessively high due to the fact that the reservoir is embedded excessively deep in hot-summer and cold-winter zones, and the underground concrete impounding reservoir is frozen in winter under the condition of not increasing the embedded depth in cold and severe cold regions with the frozen soil depth being larger than 1,000 mm.