Systematic sedimentary mircofacies research has never been done in Quan 1 section that is the principal section of Fulongquan gas field located in the south Songliao basin. The authors start with core analysis and regional geological data, logging data, using petrologic phase and electrofacies switching technology to divide and compare the sedimentary mir- coracles of the Quan 1 section in the area, first put forward braided river deposition system. And therefore to further recognize sedimentary mircofacies such as channel lag, mid-channel bar crevasse splay, flood plain, establish vertical sedimentary sequencesthe of braided river, study on the planar distribution characteristics, provide an important basis for prediction of sand body distribution and reservoir 3-d attribute modeling, provide necessary warrant for high effective development of Fulongquan gas field.