Abstract: This paper discusses theorectically the three stress states of the nylon ball in the separate-layer fracturing:the ball will deviate from the centre flowline and tend to the pore when the inertia force is smaller than the drag force;the ball will set on the pore and ensure the successful operation in fracturing when the force keeping the ball on the pore is larger than the impact force caused by the liquid flow;after pumping off,the holding force is zero,the force produced by the formation pressure will drop the ball into the bottom hole from the pore.According to the practical well temperature log and the recorded operation curves in fracturing,this paper discusses the feasibility of setting ball separatelayer fracturing,analyses the results of different fracturing schemes,and provides the full application basis in theory and practice for the selection of setting ball fracturing of seprate layers.