The carbonate platform and trough facies of the Late Permian to the Early Triassic Feixianguan Formation are outcropped in the east Fankuai in Xuanhan County, northeastern  Sichuan Basin. The distance between the Jichang carbonate slope facies section which separates the platform facies and trough facies， and the platform margin facies section is less than one kilometer. According to the characteristics of the outcrops of carbonate slope facies，  the carbonate slope facies can be identified on the seismic sections of KaijiangLiangping trough in northern Sichuan Basin and the shallow water carbonate sedimentary area and deep water carbonate sedimentary area was subdivided. Slope facies is characterized by the obvious inclined reflection. High amplitude reflection caused by the mudstone of Dalong Formation and the bottom of the Feixianguan Formation of the trough facies onlapped towards the platform and disappeared. The twoway travel time of trough facies in the Upper Permian is less than 100 ms and is far less than that of the Feixianguan Formation， while the twoway travel time of platform facies is more than 150 ms which is similar to or slightly longer than that of the Feixianguan Formation. The incline reflection characteristics of slope facies,  indicate that the carbonate slope of KaijiangLiangping trough was developed in the middle Late Permian and migrated to the carbonate platform with transgression occurred. It became the steepest slope when the transgression reached the maxium at the end of the Late Permian. In the Feixianguan Period， slope gradient decreased with the sea level fall and the slope migrated to the trough. At the end of the Late Permian， the slope gradient of Liangping area which is the south of the trough was around 3°and slope became steep towards the northeast and northwest. In the Xuanhan area， the slope gradient was about 20°， and it achieved the highest gradient of  40° in Yilong area. The trough was a basin which became deeper to wards the north. According to the height of the inclined reflection of slope in the Late Permian， it is calculated that the depth of the KaijiangLiangping trough was around 350 to 450 meters. The slopes are characterized by obvious progradation of the Feixianguan Formation in Cangxi， Yilong and Liangping areas and the slope is dominated by aggradation in Xuanhan area. The currently drilled thickest oolitic beach reservoir is located in the platform margin adjacent to the aggradational slope in Xuanhan area. The thickness oolitic dolomite reservoir in individual wells is larger than 300 meters.