The application provides a self-locking ball seat, which comprises an opening sleeve, a
ball catching cylinder, a pressure receiving seat and a stopper, all of which are arranged in a shell; the
ball catching cylinder is arranged in the opening sleeve and connected with the opening sleeve through a first fixing part; the opening sleeve is connected with the shell through a second fixing part; the lower part of the
ball catching cylinder is connected with an elastic member; the stopper is connected with the pressure receiving seat through a third fixing part, and the stopper is in contact with the side wall of the opening sleeve; the pressure receiving seat has a channel extending from the pressure receiving seat to the upper part of the ball catching cylinder; the first fixing part is
cut off, so that the ball catching cylinder moves downward and compresses the elastic member; the second fixing part is
cut off, so that the opening sleeve moves downward and pushes the stopper to move radially inward; the stopper cuts off the third fixing part and moves radially inward to a position; the ball catching cylinder and the ball can move upward; the side wall of the ball catching cylinder is in contact with and sealed with the inner wall of the channel, and the ball is in contact with and limited by the lower surface of the stopper. The application can prevent
cement slurry from returning, realize self-locking sealing of the ball seat and improve
well cementing quality.