Abstract: A series of Ta(5 nm)/Ni81Fe19(20 nm)/Ta(3 nm) magnetic thin films were prepared by magnetron sputtering method. Effects of substrate temperature and buffer layer thickness on the structure and magnetic property of Ni81Fe19 thin films had been investigated. The film structure and grain orientation were analyzed by X-ray diffraction; Resistivity and AMR value of Ni81Fe19thin films were measured by four-point probe technology. Magnetic hysteresis loop was measured by FD-SMOKE-A. The results showed that, the Ni81Fe19 films prepared at the substrate temperatures of 400 ℃ showed a higher AMR value and a lower saturation magnetic field. The highest AMR value was 3.5% and the lowest magnetized saturated field was 739.67 A/m. The Ni81Fe19 films prepared at the substrate temperatures of 500 ℃ showed the highest saturation magnetization value. With the increase of the buffer layer thickness AMR value improved first but then decreased. It reached the maximum when the buffer layer thickness x was 5 nm.