Abstract：The Cenozoic Qaidam Basin has complex sedimentary characteristics, rapid transition of sedimentary facies and various types of lithology. The authors made a systematic analysis of the lithologic characteristics of the overlying strata of the bedrock in the North Kunlun step-fault zone from geological background, core characteristics and microscopic characteristics, and concluded that the sediments are residual-slope sediments. The new understanding of the residual-slope sediments has added a new type of oil and gas reservoirs for oil and gas exploration in the Qaidam Basin and pointed out a new direction for oil and gas exploration of the overlying strata in the bedrock of Qaidam Basin.