Study on the period changes of XY Leonis

XY Leo (BD+18 degrees 2307, p = 0(d).28) was observed each season from 1992 through 1995 at Yunnan Observatory with the 1 m telescope and 37 new helio centric times of minimum light were determined. The newly expanded database of the minimum times,including these new epochs, definitely confirm the si ne-like variation of its O-C values. Observations and analyses strongly sup ported the viewpoint that the variation of the O-C values of the minimum ti mes is mainly caused by the light-time effect. Based on this newly expanded database, new light elements for the eclipsing system XY Leo and new light -time orbit for this complex system have been obtained with much better acc uracy than before by means of the least squares fitting to the light-time e quation. It's also noted that the additional period variation for XY Leo pr obably may not be ruled out besides the light-time effect. The method of an alysis and the discussion of the results are presented in this paper.