The Middle to Late Ordovician is an important period with abounding deep-water contour current activities in the western margin of Ordos Basin，and contour currents have significant impact on the morphological characteristics of reservoir and the distribution of hydrocarbon source rock in oil and gas systems. The Lower Kelimoli Formation in Zhuozisan area of Inner Mongolia was taken as an example in this paper，and the characteristics of contour current was analysed according to the previous studies and the oxygen and carbon isotopic test data of thin-bedded limestone. The results show that the thin-bedded limestone of Kelimoli Formation is deposited in a normal salinity seawater，where an oxygen isotope exchange balance exits between seawater and limestone during the limestone deposition，and the effect of limestone diagenesis on oxygen isotope is negligible. The paleo-water temperature measured according to the oxygen isotope data is in the range of 22.2 ℃ to 30.7 ℃ with an average as 26.4 ℃. According to the characteristics of high temperature and normal salinity of deep water during the sedimentary period，it is inferred that the Lower Kelimoli Formation in the study area may be isothermal current deposits caused by wind-sea currents，which belong to the surface ocean circulation. This discovery suggests that the Lower Paleozoic in western margin of Ordos Basin may develops self-generation self-storage contour current oil and gas reservoirs with a broad prospect of hydrocarbon exploration.