The utility model discloses an experimental device for preparing nano-silver by a controllable injection speed reduction method. The device comprises a bottom plate, a supporting plate is fixedly connected to the upper surface of the bottom plate, a bearing is fixedly connected to the upper surface of the supporting plate, a threaded cap is connected into the bearing in a sleeved mode, a first gear is connected to the outer surface of the threaded cap in a sleeved mode, and the first gear is located on the rear side of the bearing. The utility model discloses an experimental device for preparing nano-silver by a controllable injection speed reduction method. A first gear, a second gear, a first servo motor, a second servo motor, a sliding rod, a sliding sleeve, a threaded column and a storage cavity are arranged; a first servo motor is controlled to work to enable a second gear to rotate forwards; the second gear drives the first gear to rotate reversely, the first gear drives the threaded cap to rotate reversely, and therefore the injection rate of PVP can be adjusted at different rates, the situation that the concentration of PVP in a reaction system exceeds the standard or doesnot meet the requirement is avoided, and the preparation success rate of nano-silver is increased.