Abstract: Seven cultivars and one line of spring safflower (Carthamus tinctorius L.) were used to estimate genetic variation, heritability, genetic gain and genetic factor analysis for several physiological traits. Each experiment was conducted in a randomized complete block design with three replications. Factor loadings in first factor were used for determination of important physiological traits for suitable genotype screening under each irrigation regimes. Under non-stress conditions, factor analysis technique extracted six factors which exploited about 93% of the total genetic variation, while 30% of the total genetic variance was associated by the first factor. Under stress conditions factor analysis extracted four factors and they totally explained 100% of the total genetic variation, while, the first factor accounted for 38% of the total genetic variation. Ultimate, leaf area index (at stem-elongation and flowering), leaf osmotic potential (at stem-elongation) and rate of water loss from excised leaves (at flowering) under non-stress conditions and also leaf area index (at flowering and grain filling) and rate of water loss from excised leaves (at grain filling) under stress conditions were the best criteria for screening of suitable genotype under explicated conditions.