Using comparative analysis method, by dissecting Yacheng Formation in Yabei Sag carefully，the authors know sedimentation and source rock characteristics of Yacheng Formation in Beijiao Sag. Combined with drilling wells’ geochemical index, geothermal characteristics, reservoir-caprock assemblage, the authors evaluated the exploration potential of Beijiao Sag and obtained the following conclusions. Drilling wells have proved Beijiao Sag can form highly mature coal-derived gas and there are many sets of reservoir-caprock assemblages around the sag. This sag has good exploration potential.