Downhole anti-falling device and screw drill

The invention discloses an underground anti-falling device and a screw drill, and relates to the technical field of underground petroleum drilling, the underground anti-falling device comprises a hollow shell part, a limiting step is arranged in the hollow shell part and divides a cavity of the shell part into a lower cavity and an upper cavity which are communicated with each other, an overflowing hole is formed in the limiting step, the lower cavity is used for being in butt joint with a motor, and the upper cavity is used for being in butt joint with the motor; a static valve part is arranged in the upper cavity; the movable valve rod is connected with a rotor of the motor, a movable valve plate located in the upper cavity is arranged on the movable valve rod, the movable valve plate and the side, close to the motor, of the static valve part are arranged in a spaced mode, and the movable valve plate and the static valve part are matched to form an overflowing channel; when the rotor is tripped and falls of