Abstract: The unloosening screw of national standard is limited by its inherent structure, the screw is easy to be broken or the thread is damaged. The design of floatable unloosening screw components breaks the limits of the national standard, a floatable nut is used in its structure, and the dimensions of critical parts also increased. The analysis, simulation and engineering application of floatable unloosening screw components proves that assembly tolerance has been increased to more than double its original one, and the strength of the screw has also been greatly improved, the problem of screw breakage and thread damage can besolved effectively.