(Ni78Fe22)1‐x‐Tbx thin films (30 nm) were prepared by DC magnetron sputtering at room temperature. Their structures and magnetic properties were studied using X‐ray diffraction (XRD), vibrating sample magnetometer (VSM), and ferromagnetic resonance (FMR). The film structure changes from polycrystalline to amorphous when Tb content is around 6.9%. The magnetization is reduced with the increasing Tb content due to Tb atomic moments align antiparallel with permalloy moments, while the low coercivity Hc less than 10 Oe, and the high hysteresis squareness along the in‐plane easy‐axis is remained. The measurements of angular dependences of ferromagnetic resonance field, as well as the theoretical fitting find the surface perpendicular anisotropy constants changes from “easy” film plane to “easy” film normal and g value shows increases with increasing Tb content, which implies the increase of orbital moment with Tb dopant. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)