Nanocrystalline Pt (nc-Pt) thin film was prepared by R. F. sputtering on liquid N2 cooled substrate. Transmission Electron Microscopy (TEM)analyses clearly show that the as prepared film is constructed by numerous nanometer sized particles with average diameter of about 8-9nm. The interfaces between particles can be clearly seen and the interface width is about nmm. Electron Diffraction (ED) photograph and X-ray Diffraction (XRD) spectroscopy both confirm that the nanometer sized particles in the film are ultra fine crystallites with a cubic structure. The crystallite size increases gradually with annealing temperature. The temperature coefficient of resistance (TCR) of nc-Pt film are much lower than that of polycrystalline Pt film. DC conductivity and TCR also increase gradually with the increase of annealing temperature. It is suggested that the interfaces between the nanoorystallites greatly influence the properties of nc-Pt thin film.