Peach powdery mildew (Podosphaera pannosa) is one of the most economically destructive diseases of peach all over the world including Iran. If suitable environmental conditions are provided, this disease will damage nectarine trees more than any other disease and will reduce the yield, reduce fruit quality and increase production costs. In order to evaluate 11 genotypes of nectarines reaction against powdery mildew, an experiment was conducted in randomized complete block design with three replications during 2017-2018 in Agriculture and Natural Resources Research Station in Meshginshahr. The research was conducted in two conditions of natural infection and artificial inoculation. Cultivars included Independence, Stargold, Sangold, Sangold, Sanking, Giuta, Shabrang karaj, Ghermeze Paeeze karaj, Vega, Orion, Jiova and Veinberger. Evaluation of different cultivars of nectarine reaction to powdery mildew was conducted follow: 0: Immune, 1: Very resistant 2: Resistant 3: Medium resistant 4: Sensitive and 5: Very sensitive. The results of two-year evaluation showed that there were significant differences between the degrees of resistance among the treatments. Comparison of means showed that the cultivar Veinberger in resistant and Stargold, Sangold, Sangold, Sanking, Giuta, Shabrang karaj, Ghermeze Paeeze karaj, Vega, Orion and Jiova were in medium resistant cultivars. In general, 9% of the studied cultivars were resistant and 91% were moderately resistant to peach powdery mildew. Comparison of means showed that the cultivar Veinberger in resistant and Stargold, Sangold, Sangold, Sanking, Giuta, Shabrang karaj, Ghermeze Paeeze karaj, Vega, Orion and Jiova were in medium resistant cultivars. In conclusion of this study, it can be said that the use of resistant cultivars is the best method of controlling P. Penosa powdery mildew. In order to reduce the damage of the fungus causing the disease, production and application of resistant nectarine cultivars is recommended as the most important method of control.