Abstract: Based on the characteristics of heavy mineral combination, seismic facies, wave impedance inversion, the single well and multiwell facies section as well as the high?resolution sequence stratigraphy, the sedimentary provenance and sedimentary facies of the second member of Xiazijie formation in Bai?21 well block in Junggar basin are analyzed. The result shows that the Xiazijie formation developed an alluvial fan and the sedimentary provenance is in direction of north to slight west; the second member of the Xiazijie formation developed five sedimentary cycles, the lower two cycles are dominated by braided stream channel deposit and the upper three by lateral margin of braided stream zone and over bank sand, reflecting the reducing process of the fan sedimentary scope