Abstract: In Early Paleozoic, the Tarim Basin was a craton basin with diverse deposits, where tectonic movements and eustatic sea-level changes dominated the development of Cambrian and Ordovician sequence formations. Integrated with outcrop, core, well logging and seismic data, we identified 15 sequence interfaces in the Cambrian and Ordovician of the Tarim Basin and divided the Cambrian into 6 sequence formations and the Ordovician into 8 sequence formations. Based on characteristics of these sequence formations and in view of the importance of faults and unconformity interfaces in hydrocarbon migration and accumulation, petroleum systems of Cambrian and Ordovician sequence frameworks in the Tarim Basin were divided into three different types, the continuous, discontinuous and complex. In practice, the exploration of petroleum systems includes continuous or discontinuous source-reservoir-cap rock combinations with lateral changes and the exploration of potential source-reservoir-cap rock combinations encompasses also continuous or complex source-reservoir-cap rock combinations characterized by an upper source-middle reservoir-upper seal play. It is worth exploring continuous or enclosed-continuous source-reservoir-cap rock combinations characterized by a lower source-middle reservoir-upper seal play.