Abstract: Ball-activated sleeve plays an important role in open hole staged fracturing,which may determine number of fracturing stages and flow channels.However,studies have not been initiated in China on sealability between ball and ball seat,drillability and erosion resistance of ball seat.In this paper,finite element analysis and experiment were conducted in respect to structural design of ball seat,selection of ball materials,and sealability between ball and ball seat,so as to find appropriate sealing techniques.Optimization of ball materials and relevant tests were made to identify the drillability of ball seat.Additionally,surface hardening of ball seat was discussed,together with corrosion and sealing experiments,to analyze the corrosion resistance of the ball seat.This ball-activated sleeve technique was applied in 8 wells in 72 fracturing stages,proving that it was reasonable and reliable,and could be effectively used for sealing under high pressure and entire drifting of completion string.