Abstract: The middle-lower Jurassic in Turpan Sag is divided into six third class sequences and ten fourth class sequences by using the theories and methods of high-precision sequence stratigraphy and comprehensive studies of the outcrop section, drilling/logging and seismic data, being a research process including the division of sequence stratigraphy of the outcrop section, the identification of sequence surface of drilling/logging,the division and correlation of sequence stratigraphy among the wells, and the division of sequence stratigraphy of seismism. The fourth class sequence of the sag approaches the natural sedimentary cyclothem, the low of which is mainly consisted of the distributary channel sandstones including the lamina argillites in the fluvial facies or the braided river delta facies, and the top of which is mainly consisted of the argillites including the lamina sandstones in the shore and mere facies. On the basis of the study a high-precision sequence framework of mlddle-lower Jurassic in Turpan Sag is established, which is very important for looking for lithologic hydrocarbon reservoirs.