This paper analyzed the mouth bar in the E31 Ⅰ-11 sublayer in YuejinⅡ Oilfield of Qaidam Basin by using well logging, geological data and application configuration analysis. The research suggests that there developed two mouth bars, two kinds of configuration units and five accreting bodies in the E31 Ⅰ-11 sublayer. Mouth bar is limited by restraining barrier as the identification of fifth interface,between accreting bodies is mudstone interlayer as the identification of fourth interface. According to the research of the configuration units combination in space, splicing between two mouth bars, mouth bar and sheet bar splicing, and mouth bar lateral accretions exist in the direction vertical to the source, and mouth bar progradation and retrogradation exist in the direction parallel to the source. There are aggradation-positive cycle and aggradation-reverse cycle between configuration units on the vertical. Reverse rhyme is the main characteristic in configuration unit, followed by positive rhythm. On the basis of the above research, the plane distribution map of five accreting bodies was completed.