The invention discloses a speed reducer drill and motor magnetic coupling overturning and feeding mechanism. The speed reducer drill and motor magnetic coupling overturning and feeding mechanism comprises a main substrate, a guide bracket, a pair of driving sliding plates, a drill assembly and a motor assembly, wherein a sliding notch is formed in the main substrate; the guide bracket is arranged in the sliding notch, and the guide bracket comprises a pair of parallel guide base plates; the drill assembly is rotatably arranged between the guide base plates; the motor assembly is movably arranged between the guide base plates; and the drill assembly is separably connected with the motor assembly through magnetic coupling, and the drill assembly and the motor assembly are synchronously driven by the driving sliding plates, so that the drill assembly and the motor assembly are connected or disconnected. According to the speed reducer drill and motor magnetic coupling overturning and feeding mechanism, a motor is separated from a speed reducer and is connected with the speed reducer through the magnetic coupling. If balance oil in the speed reducer leaks, external high-pressure mud invades the speed reducer, but the motor and a control system cannot be damaged.