Single-layer Fe_ x Ni_1 - x thin magnetic films have been investigated by the spin-wave resonance technique in the entire concentration range. The surface anisotropy and exchange stiffness constants for the films with a Ni content from 30 to 80 at % have been measured from the experimental standing spin wave spectra. The surface exchange spin wave penetration depth δ_ C = 20–30 nm has been determined from the dependences of the surface anisotropy and exchange coupling constants on the Fe_20Ni_80 film thickness in the range of 250–400 nm.