The invention relates to a ballscrew nut mounting structure which comprises a nut seat which is connected with a workbench and a screw nut which has a flange and penetrates through the nut seat, wherein a magnet is embedded in the nut seat or the flange of the screw nut, and the screw nut is connected onto the nut seat through a flange face and the magnet. The ballscrew nut mounting structure has a simple structure, and is convenient to install. During the ballscrew assembly, not only is the mounting precision ensured, but also the assembly requirement is simplified. Moreover, the ballscrew nut mounting structure also can be used as a protection device for preventing a machine tool from collision.