Molecular Dynamics (MD) simulations have been carried out on pure ultrathin Nickel (Ni) crystal with face-centered cubic (FCC) lattice upon application of uniaxial tension at nanolevel with a speed of 20 m/s. The deformation corresponds to the direction . To the calculated block of crystal - free boundary conditions are applied in the directions , . Morse potential was employed to carry out three dimensional molecular dynamics simulations. A computer experiment is performed at a temperature corresponding to 10 K, 300 K and 1000 K. MD simulation used to investigate the effect of long of ultrathin Ni nanowire on the nature of deformation and fracture. The engineering stresstime diagrams obtained by the MD simulations of the tensile specimens of these ultrathin Ni nanowires show a rapid increase in stress up to a maximum followed by a gradual drop to zero when the specimen fails by ductile fracture. The feature of deformation energy can be divided into four regions: quasi-elastic, plastic, flow and failure. The results showed that breaking position depended on the nanowire length.