Natural and artificial selection that has been made on bread wheat during thousands of years, caused the loss of part of the original genetic diversity which were inherited from its ancestors. Therefore, breeders seek to study the ancient ancestors of wheat to transfer lost genes such as resistance to biotic and abiotic stresses through synthetic wheats. Synthetic wheat has been obtained from the cross between tetraploid wheat (Emer and Durum) with Aegilops tauschii . Ae. tauschii genome (D) contains resistant genes to various biotic and abiotic stresses which could make synthetic wheat more resistant to most of stresses, such as drought stress. In this study, synthetic wheat genotypes were evaluated in the field of Isfahan University of Technology in order to study genetic diversity, drought tolerance and the effect of drought stress memory. Twenty seven wheat genotypes including 20 synthetic hexaploid wheat, 4 common hexaploid Iranian bread wheat and 3 foreign bread wheat genotypes were evaluated under four moisture environments (N, S, D 1 D 2 and D 2 ) (control moisture environment, seed stress-reproductive stress, vegetative stress-reproductive stress and reproductive stress, respectively) as a combined experimental analysis design according to a randomized complete block design with three replications. The results showed that the studied wheat genotypes in terms of grain yield, yield components (number of spikes, 1000-seed weight, harvest index) and physiological traits had a wide range of variation in all four wet environments. Synthetic wheat genotypes were significantly superior to the common wheat (Iranian and foreign) genotypes in terms of yield, yield components and drought tolerance. The results also showed that drought stress significantly reduced yield and yield components under three stress moisture environments (S, D 1 D 2 , D 2 ) compared to normal environment (N). However, this yield reduction was different in stress moisture environments (S, D 1 D 2 , D 2 ), which was about 43%, in seed stress- reproductive stress (S) moisture, 35% in vegetative stress-reproductive stress (D 1 D 2 ) 47% in reproductive stress (D 2 ) compared to the control (N) condition. As the results show, the lowest yield reduction was related to the vegetative stress- reproductive stress (D 1 D 2 ). The main difference between this moisture treatment with other moisture treatments (S and D 2 ) is in the initial stress (D 1 ) which was applied on it (D 1 D 2 ). The effect of initial stress (D 1 ) on physiological measured traits during recovery (irrigation after stress) and the end of the reproductive stress period was also quite evident. For example, there was a significant difference at recovery period (irrigation after stress) for some traits such as the activity of antioxidant enzymes (ascorbate, guaiacol peroxidase) and proline, in moisture treatment (D 1 D 2 ) compared to the control treatment (N). It seems that mild primary drought stress (D 1 ) has activated the plant's physiological defense system, creating a kind of cellular readiness that will help the plant perform better than a plant which has only seen reproductive stress. Furthermore, final sampling after applying reproductive stress (D 2 ) showed that the moisture treatment (D 1 D 2 ) had a more activated antioxidant system than the moisture treatment (D 2 ). In fact, initial stress has led to the induction of drought stress memory mechanism, and subsequently yielded improvement of genotypes under the subsequent (second) drought stress. The results of correlation showed that yield components (number of spikes, 1000-seed weight, harvest index and biological yield) had a positive and significant association with grain yield under four moisture treatments. These relationships can be used to define selection criteria. In addition, in four moisture treatment, phenological traits were negatively correlated with grain yield and yield components under four moisture environments. The negative correlation between day to pollination and grain yield indicated that selection for early maturity under stress conditions may lead to improve drought tolerance. Based on the grain yield, and yield components, drought tolerance index and physiological traits, synthetic genotypes with codes 200, 80 and 58 were known as the best genotypes with favorable performance under four wet moisture environments. Overall, the results showed that due to the arid and semi-arid climate of the country and the strategic nature of the wheat crop, the need to use synthetic cultivars in wheat breeding programs is evident. Keywords: Genetic diversity, Synthetic cultivars, Drought stress, Stress memory