Among perovskite manganese oxide systems, La1-xSrxMnO3, has been intensely investigated because of its interesting magnetic and electronic properties such as colossal magneto resistance (CMR). These properties are largely determined by the electronic structure of the valence electrons. The electronic structure of the electrons in the energy states near the Fermi level was probed by using electronic excitations of less than a few eV. Ordinarily, the information obtained about the energy states was integrated over all crystal orientations, and only few anisotropic systems were studied in terms of their orientation dependence. In the present study, we reported an orientation dependence of the plasmon dispersion, which corresponded to electronic excitations of 30eV and characterized the collective excitation of the valance electrons, on an isotropic system La,.xSrxMn03 (x=0.4) by angular-resolved electron energy loss spectroscopy (EELS).