An anti-loosening cylindrical threaded part includes internal and external threaded part. A cylindrical internal thread is arranged in inner hole of internal threaded part a cylindrical external thread is arranged on a screw of external threaded part, the inner hole of internal threaded part has cylindrical surface parallel to a longitudinal center axis of internal thread, and an inner diameter of cylindrical surface is greater than minimum inner diameter of internal thread. Surfaces of internal and external thread and cylindrical surface are not covered with anti-loosening materials. After internal and external thread are mutually screwed, cylindrical surface and a crest of external thread are mutually close contact structures, that is, a horizontal locking structure; therefore, loosening can be effectively prevented between cylindrical internal and external threaded part without longitudinal contractility of threaded part and a workpiece, and presently suitable for loosening prevention in various connections of the cylindrical threaded parts.