Abstract: Based on the data of well logs,seismics,core and regional geology,the types and characteristics of valley-slope in the BZ3 area were studied in detail,with focus on analyzing the control effect of different type of slope-break zone over the depositional system under the base-level cycles.The favorable areas for hydrocarbon exploration were also predicted primarily in this paper.The results show that there are three types of valleys,i.e.U-shape,V-shape and W-shape valleys,and three slope-break zones,i.e.high,low and flexure ones in the BZ3 area.The delta-front facies developed on the terrace Ⅰ and the low-stand fan developed on the terrace Ⅱ are the favorable areas for reservoir development.