The Ordovician strata in Keping area of Tarim Basin are dominated by a series of stable carbonate and clastic rocks and can be divided into shallow platform and deep water depositional systems and then subdivided into four different facies types, namely, restricted platform, open platform, neritic shelf and basin. Based on detailed outcrop geological research, the authors found two different kinds of sequence boundaries, i.e., partially exposed unconformity sequence surface and drowned unconformity sequence surface. The partially exposed unconformity sequence surfaces are mainly developed in Lower Ordovician Penglaiba Formation and Yingshan Formation. In this period, shallow-water carbonate platform was mainly developed in the study area, and small-scale sea-level fall could result in partial exposure and erosion, thus forming sedimentary discontinuity surface. As for the causes, such partially exposed unconformity sequence surfaces belong to Type Ⅱ sequence boundary. Drowned unconformity sequence surfaces were mainly developed in Middle-Upper Ordovician, and there were mainly developed two types of surfaces in the study area, i.e., platform drowned and neritic shelf drowned unconformity sequence surfaces. Based on the above study, the authors divided the Ordovician strata into 9 thirdgrade sequences according to an analysis of the sequence stratigraphic framework. Among them, the Penglaiba Formation is comparable with two third-grade sequences, the Yingshan Formation is also comparable with two third-grade sequences, the Dawangou Formation is comparable with one third-grade sequence, the Saergan and Kanling Formations are also comparable with one third-grade sequence, the Qilang Formation is comparable with two third-grade sequences, and the Yingan Formation is comparable with one third-grade sequence. The average age of the third-grade sequence is 3.67 Ma, which constituted nine times of obvious rise and fall of the sea-level. C isotopic and element geochemical compositions of those sequences suggest that δ13C values and element geochemical compositions show obvious differences and regular variations in different sequence boundaries and different sequence system tracts. The δ13C values in the sequence interface are on the whole low. In the Internal sequence, the δ13C values change from low to high and then to low again, ranging from the transgressive system tract to the highstand system tract, and the C isotope values reach the maximum within the maximum flooding surface. It is suggested that the rise and fall of sea-level occurred many times. In the study area, element geochemical features and sedimentary sequences have a good response relationship. Invariable elements and trace elements are both low in the phase region of shallow water. With the deepening of the water, Fe, Mn, Sr and Ba values show a rising trend. In the phase region of deep water, the response characteristics of element geochemical features and the sedimentary sequences are obvious. As a result, C isotope and element geochemistry can provide some quantitative geological and geochemical evidence for analyzing the Ordovician sequence.