Abstract: Soluble carbohydrates (sugars) are considered as important metabolites in plants under drought stress. In order to study the trend of changes of this osmolyte when encountering with dryness, the seeds of two species of Haloxylon persicum and Haloxylon aphyllum were planted in vase and their grown twigs underwent drought stress after a one year care and a one month compatibility with the greenhouse environment. The study of changes of this osmoiyte in branchlet and roots of the twigs of these two types of haloxylon was planned within the format of a completely randomize design with two treatments of species and fifteen tension treatments (lack of irrigation of twigs). The Two Species of Haloxylon persicum and Haloxylon aphyllum and the levels 0 (control), 2, 4… and 28 days of lack of irrigation were determined as treatments of experiment. The analysis of data in two sides analysis variance was conducted and the averages were compared by using Duncan’s test. The study of data of branchlet and root showed that with the possibility of 99%, the effect of drought stress on the increase of the rate of soluble sugar of branchlet and root of both types of haloxylon was meaningful. In addition, between these two species at the same level of reliability, there was a difference. The study of the effect of drought stress on changes of the quantities of total soluble sugars showed that the changes of this factor are of more similarity with changes of soluble sugar of root and they almost obey the same model. The increase of rate of branchlet soluble sugars, root and total soluble sugars were in proportion with the intensity of tension.