In order to assess the allelopathic effects of aerial parts residue of safflower genotypes, a set of experiments was performed during August 2013 through June 2014 in the laboratories of Agromomy and Plant Breeding department, faculty of agriculture, Isfahan University of Technology. First experiment was performed in order to survey the effect of normal irrigation and drought stress on the allelopathic potential of safflower genotypes and the second experiment was designed based on sandwich method to evaluate the allelopathic effect related to aerial part residues from 4 selected genotypes following screening in first experiment on growth of sesame, wheat, safflower, wild barley and tumbleweed, as follow. Certain amount of plant residue from donor species was spread as a layer in Petri dish. Then 5 ml of agar medium (0.5 %, without nutrients) was poured on this layer and after its solidification the second layer was formed as above described. Finally the recipient plant seeds were put on the prepared culture; the Petri dishes were sealed and incubated in defined temperature and light. In third experiment in order to find the allelopathic effect of safflower residues produced under normal irrigation and drought stress a Pot experiment and in soil environment was regarded. It was found in first experiment that drought stress increased allelopathic potential of residues. Among the cultured genotypes under drought stress, Australia (PI 262424) and Kermani (CTNIR9) genotypes had the minimum inhibitory effect on radicle length, Kermani (CTNIR9) genotype had minimum inhibition on seedling length, the least inhibitory effect on wet weight of seedling was observed in case of Kermani (CTNIR9), Australia (PI 262424), Iran (Marand), Bangladesh (PI 401470), Syria ( PI 386173) and Greece ( PI 254976) genotypes and the Australia, Kermani and Greece genotypes had the least inhibitory effects on seed germination. The Khorasan (Khorasan330) and Egypt ( PI657800) genotypes had the most inhibition on radicle length and Cyprus (PI533619) variety showed maximum inhibition for wet weight of seedling and seed germination. Furthermore, from the cultured genotypes under normal irrigation, Khorasan (Khorasan330) and Egypt (PI657800) genotypes showed the most inhibitory effects while Australia (PI 262424) and Kermani (CTNIR9) genotypes had the minimum inhibitory effects. The results of second experiment were confirmed the results of first experiment. It was revealed in this experiment that as small as is the plant seed, target seedling will show more sensitivity to the residue's allelopathic effects. As a result, among the studied plants, tumbleweed and safflower showed most and least sensitivity to safflower residues, respectively. Furthermore, it was determined that radicle length in comparison with other parts of seedling has more sensitivity to allelochemichal substances. The results of pot experiment suggest that root residues of safflower genotypes have the most allelopathic activity. Application of safflower residues in soil caused reduction of shoot length, wet weight and germination percentage of raddish which the residues of cultured plants under drought stress had more allelopathic potential. In addition, it was found that plant exposure with allelochemichal cause increasing its anti-oxidant enzymes. So, most antioxidant enzymes activity was found i seedling that were cultured in the presence of root residue of safflower genotypes and under drought stress. Keywords : Allelopathy, Sandwich method, Drought stress, Allelochemichal, Anti-oxidant enzymes