A spectral study of the Be/X-ray binary LSI+61 degrees 303

New optical intermediate dispersion spectra of the periodic radio star LSI +61 degrees 303 are presented. The H-alpha emission line shows a typical sh ell absorption spectrum, which means that the primary of this Be/X ray bina ry may be a nearly equator-on Be star. The H-alpha emission line profile an d its variation are analyzed, and some parameters such as the H-alpha EW an d V/R peak ratio change strongly near the radio maximum, and may exhibit pe riodic variability. instead of having a wider minimum lasting for about hal f an orbital cycle as radio flux and V magnitude do, the H-alpha EW shows a deep minimum at phase similar to 0.75. The accretion disk around the neutr on star formed near its periastron passage is suggested to be responsible f or the change when it eclipses the primary and its envelope.