Photometric observations of an eclipsing binary system , YY Eridani were done in blue (B) and yellow (V) wavelength bands and , finally , the light curve in each wavelength band was constructed.

Orbital elements and physical properties of YY Eridani have been calculated using observational data of Binnendijk(1965) and authors have developed Wilson-Devinney technique in analyzing the best solution of this eclipsing binary system.

Synthetic light curves which were constructed from the best solution are in good correspondence with observational light curves of Binnendijk. When comparing with observational light curves obtained from this research , it was found that there exist the phase shift of 0.1. It is possible that physical properties of YY Eridani have been changed due to rotation of its major axis or mass transfer mechanism of the system.

Key Words : eclipsing binary system , YY Eridani , Wilson-Devinney Technique , photometric observation.