The utility model discloses a precision assembling device for a medical assembly. Limiting mouths are formed in circular internal tooth threaded sleeves in the circumferential direction. The precision assembling device comprises a base, a flip cover plate, a first rotating cover plate and a second rotating cover plate, wherein the flip cover plate can rotate around a second rotating shaft. Grooves of the base are provided with square channels, and the square channels are communicated with the grooves through a plurality of through strip holes. The working surface of the first rotating cover plate is provided with a plurality of circular through holes used for containing the circular internal tooth threaded sleeves, and at least two protruded points are distributed on the peripheries of the circular through holes. One limiting protruded strip is located on the working surface of the first rotating cover plate and on the edge of the corresponding circular through hole, and the diameter of each circular through hole is located between the external diameter and the internal diameter of each circular internal tooth threaded sleeve. A plurality of strip through holes in a y direction are formed in the flip cover plate, and the second rotating cover plate is provided with a plurality of circular holes allowing external tooth threaded rods to be embedded in. According to the precision assembling device for the medical assembly, efficiency, assembling precision and stability are greatly improved, assembling labor intensity is reduced, and convenience is improved.