The interfacial properties of the ferromagnetic (FM)/ferroelectric (FE) heterostructure La0.7Sr0.3MnO3/BaTiO3 (LSMO/BTO) have been investigated by employing spin wave resonance technique. In addition to the uniform ferromagnetic resonance, spin wave resonances with both body and surface wave modes are observed. The analysis on the spin wave spectrum in comparison with that of a La0.7Sr0.3MnO3 thin film suggests that the ferroelectric BaTiO3 layer not only modifies the in-plane bulk magnetic anisotropy of La0.7Sr0.3MnO3 but also induces surface spin pinning both in plane and out of plane. Moreover, a quantitative determination of spin wave exchange constant D is obtained from the spin wave spectrum at low temperature. Our study proves that spin wave resonance is a powerful tool to investigate the buried interfaces in ferromagnetic/ferroelectric heterostructures.