Abstract: This field study was conducted in order to investigate the yield and quality of sugar beet Cv zargan in relation to sowing date and different irrigation regimes during 2005 at Ardabil conditions. The experimental design was a randomized complete block design with factorial arrangement in four replicates. In this experiment two factor with four levels were used: Sowing date (S1 = 5 Apr, S2 = 20 Apr, S3 = 5 May and S4 = 20 May) and irrigation including: I1 = Irrigation at 13.3 FC (30% FC), I2 = Irrigation at 15.5 FC (50% FC), I3 = Irrigation at 17.7 FC (70% FC) and I4 = Irrigation at 19.9 FC (90% FC). The SAS software package was used to analyze all the data and means were separated by the least significant difference (LSD) test at p<0.01. In this study adjectives such as root yield (t ha-1), leaf yield (t ha-1), sugar content (%), Molasses (%), pure sugar content (%), white sugar yield (t ha-1), Na (mmol/100 g root), K (mmol/100 g root) and α-amino N (mmol/100 g root) were evaluated. Sowing date and irrigation had a significant effect on sugar yield and its quality. Potassium concentration was not significantly affected by irrigation treatments. Interaction effects between sowing date and irrigation treatments were significant (p<0.01) for all adjectives. Both early and late sowing decreased beet root and leaf yield. Results of irrigation treatments showed that the optimum soil water content for root yield is 70% of field capacity with 66.5 t ha-1. The minimum root yield (47.36 t ha-1) observed at 90% of field capacity. Sugar content (%) affected by sowing date and irrigation treatments. However irrigation at 30, 50 and 70% of field capacity (I1, I2 and I3) had same effect on sugar content while sugar content decreased at 90% field capacity (I4). Therefore the optimum sowing date in Ardabil condition is 20 April that maximum yield and quality observed on this treatment. When the available soil water content was at 70% of field capacity, maximum root yield observed.