In this work, the phenomena of excitation of SWR (Spin Wave Resonance) in magnetic films are investigated. On the basis of Partis' Volume Inhomogeneity (Ⅵ) Model, the Asymmetric Volume Inhomogeneity (AⅥ) Model and the Surface-Volume Inhomogeneity (S-Ⅵ) Model are proposed. In terms of these models, we can explain satifactorily the linear spectra of SWE, in which the odd and even modes are excited simultaneously with their intensities changing in accordance with different envelopes.