The unconformity between Sinian and Cambrian strata is widespread developed within and around Tarim Basin. Two types of unconformities are presented in the study area based on the seismic and geological outcrop analysis. One type is parallel unconformity which locates in Kuruktag，Kalpin and the northern depression and its north area. The other type is angular unconformity which developes near the north ramp of the Central Rise(Tadong low upliftTazhong low upliftBachu fault uplift)and can be clearly identified from the eastwest trending seismic records. Palaeokarst dolomite reservoirs of Sinian were formed associated with the unconformity between Sinian and Cambrian. Beneficial direction of the Palaeokarst dolomite reservoirs of Sinian in Tarim Basin is north ramp of the central rise where the angular unconformity distributes.