Abstract: According to log data of Bandong 4 well in Changxing Formation in Bandong structure of the east of Sichuan Basin, reservoir rocks and organic reef of Changxing Formation were studied in this paper. The research indicated that there are biomicrites, reef limestones, and dolomites in reservoir rocks. By means of reservoir rock's physical property, areal logging data and field sections, model of organic reef's formation and evolution was summarized. Identification model of reservoir in Changxing Formation has been established by means of seismic response characteristics and inversion technology, and thickness distribution of reservoir was computed by computer using corresponding velocity and effective thickness of reservoir extracted by Landmark software. Compared with drilling depth, it was proved that organic reef in Bandong 4 well was point reef.