The self-locking of electric cylinder T-screw and ball screw. The electric cylinder T-screw itself has self-locking function because the thread angle is less than the equivalent friction angle. The self-locking of the electric cylinder ball screw requires the addition of a self-locking mechanism to complete. The first type of motor has a braking function; The second type of coupling between the motor and the ball screw is equipped with a power-off brake mechanism; The third type of motor is first connected to a worm gear reducer with self-locking function, and then the output shaft of the worm gear reducer drives the ball screw, which is not only troublesome, but also reduces the transmission accuracy significantly. The fourth method is to install a brake mechanism on the other end of the ball screw.