This study was conducted at Kharabo Dairy Station belongs to the Faculty of agriculture, University of Damascus. 553 records for 206 Holstein Friesian cattle were used to study factors affecting the calving interval during 1982 to 2007. Data were exposed eccording to GLM, and analysis of variance was used to determine the calving interval (CI) and the effect of calving year, calving season, parity and interactions on the calving interval, and Duncan test was used to compare means by SPSS program. The overall mean for (CI) was 459.12±4.90 days. and affected significantly (0.001>P) by calving year, but there was no significant effect for calving season, parity and interactions between studied factors on the calving interval. These results suggested that better management, and applaying more efficient administration practices as well as to improving the feeding status may reduce calving interval to typical period of 365 days and increase reproductive and economic efficiency of dairy cattle at Kharabo station.