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We report 138 spectral observations of the H-alpha emission line of theradio- and gamma-ray-emitting Be/X-ray binary LSI+61303 obtained during theperiod of September 1998 -- January 2013. From measuring various H-alphaparameters, we found that the orbital modulation of the H-alpha is best visiblein the equivalent width ratio EW(B)/EW(R), the equivalent width of the bluehump, and in the radial velocity of the central dip. The periodogram analysisconfirmed that the H-alpha emission is modulated with the orbital andsuperorbital periods. For the past 20 years the radius of the circumstellardisk is similar to the Roche lobe size at the periastron. It is probablytruncated by a 6:1 resonance. The orbital maximum of the equivalent width ofH-alpha emission peaks after the periastron and coincides on average with theX-ray and gamma-ray maxima. All the spectra are available upon request from theauthors and through the CDS.

H-alpha observations of the gamma-ray-emitting Be/X-ray binary LSI+61303: orbital modulation, disk truncation, and long-term variability