Ni-Fe alloys have various applications such as thin film inductor, thin film transformer, magnetic head’s shield case, etc. Magnetic properties of Ni-Fe thin films depend on the process parameters such as thickness, contents, deposition rate, substrates, etc. In this study, NiFe films with a thickness of about 150nm were deposited on Si(100) wafer and SiO2/Si(100) substrate at room temperature by a DC magnetron co-sputtering using Fe and Ni targets. Their phase formation and magnetic properties as a function of annealing temperature were investigated with XRD, FE-SEM and VSM. The assputtered films have BCC structure. With increasing annealing temperature, NiFe thin film for SiO2/Si(100) substrate transformed completely from BCC to FCC phase above 500oC, but some BCC phase remained above 500oC on Si(100)wafer. For samples annealed at 450oC, squareness ratio of NiFe thin film shows peak value and its saturation magnetization is around 0.0118 emu, which means that the optimum annealing temperature of NiFe thin film seems to be 450oC. The saturation magnetization of films decreased rapidly above the annealing temperature of 500oC due to phase transformation from BCC to FCC phase.