Water deficit is one of the most important environmental factors that affects plant growth and development, and limits plant production. Water deficit negatively changes the balance between the production of reactive oxygen species (ROS) and antioxidant activity, producing oxidative stress. Sodium nitroprusside (SNP) commonly used as nitric oxide (NO) donor in plants. In orther to study the effects of different concentrations of Sodium nitroprusside (SNP), on drought tolerance of Marigold, this experiment has been carried out as factorial based on a completely randomized design in a greenhouse with 9 treatments and 6 replications. Treatments including 0, 100 and 200 µM SNP and three levels of drought stress, control (FC), moderate stress (80% FC) and severe (60% F.C.). The results of morphological, physiological and biochemical parameters showed that spraying Marigold flower with a concentration of 100 µM SNP increased tolerance of Marigold flower to drought stress through the effect on physiological and biochemical parameters and improved antioxidant enzyme activity (increased catalase). The highest stem length (40.01 cm), number of flower per plant (8.83), flower longevity (29 days), leaf relative water content (66.34% ) and total fresh weight (66.09 g), and the lowest ion leakage (28.12%) was found in plants treated with 100 µM SNP.  Further, 100 µM SNP significantly increased average number of branches, leaf chlorophyll, dry and fresh weight of flower, stem and root dry and fresh weight compared with those in control.  It was found that spraying with a concentration of 100 µM SNP could be effective in increasing tolerance of Marigold flower to drought stress.