This research was conducted in order to evaluate genetic diversity, and screening the tolerant genotypes of sugar beet subjected to continuous and severe water stress in the experimental farm of Sugar Beet Seed Institute (SBSI) in Karaj in 2008. The experimental design was a randomized complete block with 6 replications. Fifteen O-Types which were tolerant to drought plus 5 (check) genotypes were evaluated. Permanent and severe drought stress started by stop of irrigation after plant establishment continued to the end of growth season. The soil water suction reached to about 4 MPa in the horizon of 0-30 cm at the end of growth period. The results of ANOVA showed that the effect of genotypes on the root yield, shoot dry weight, total dry weight, root dry weight, root dry weight/ shoot dry weight ratio, sugar yield, achievable sugar yield, sugar percentage, harmful nitrogen and sugar percentage were significant (P<0.01). Genetic diversity among the new surveyed genotypes showed drought tolerance of sugar beet genotypes. The results confirmed that under the situation of permanent and severe water stress the genotypes of G8 (O-Type 7617) and G4 (O-Type 9590) were distinguished as tolerant O-Types and may be used in the breeding program for drought stress species. In the correlation analysis, white sugar yield with total dry weight and root dry weight showed the most positive correlation coefficients. Step wise liner regression analysis was carried out, showing sugar yield, white sugar content, sugar content and root yield, as independent variables, had significant effects on white sugar yield. With respect to yield and its components, the latter 4-mentioned characteristics showed high correlation among each other. The principal component analysis (PCA) showed that five components accounted for 82.08% of total variations. The UPGMA phonogram constructed on the basis of morphological data distance shows four clusters.