An additive repair device for internal threads is provided. The device includes a moving assembly, a rotating assembly, a speed regulation assembly, a gear assembly, an additive assembly, and a connecting assembly. The moving assembly includes a drive part and a linear movement mechanism. The additive assembly is connected to the linear movement mechanism through the connecting assembly. One end, which is far away from the drive part, of the linear movement mechanism is connected to an input end of the speed regulation assembly through the gear assembly. The rotating assembly includes a clutch mechanism and a clamping mechanism. The clutch mechanism includes a clutch outer gear and a clutch inner gear. The clutch outer gear is arranged at an output end of the speed regulation assembly. The clamping mechanism is fixed to one end, which is far away from the speed regulation assembly, of the clutch inner gear.