According to regional rock assemblages and strata subdivision principle, Lengjiaxi Group can be subdivide into upper part of marine deep-water basin deposited fine clastic rocks and lower part of basin slope turbidite deposited coarse clastic rocks. The zircons from tuff interlayers of every Formation of Lengjiaxi Formation are tested by SHRIMP U-Pb dating method to constraint the sedimentary ages, which indicated that the sedimentary age of Lengjiaxi Group is between 820 to > 862 Ma, and belongs to Early Neoproterozoic.