Field experiments were conducted based on ten Egyptian barley cultivars (Giza 2000Giza123, Giza 126, Giza 130, Giza131, Giza 132, Giza133, Giza134, Giza 135, Giza 136) sown in pure stands No fungicide was used, and under natural infection. we carried out field tests throughout two seasons of growth at Giza station in 2021 /2022 and 2022/2023, environmental conditions made it a hot spot for powdery mildew. Barley powdery mildew disease caused by a biotrophic air-born fungus Blumeria graminis f. sp. hordei. It is the most widespread disease in most barley cultivars worldwide. The results showed that six barley cultivars (Giza 131, Giza 132, Giza 133, Giza134Giza135and Giza 136) showed an adequate level of powdery mildew disease resistance during this study as they recorded a small percentage of disease severity did not surpass 50.5, and the AUDPC's lowest values (less than 300), whereas the barley cultivars; Giza 123, Giza 126, Giza 130 and Giza 2000 displayed high susceptibility to powdery mildew disease. High percentages of disease severity reached (59.5) and the high area under the disease progress curve (AUDPC) estimates more than (345.4). The research evaluates the relationship between disease severity and various grain yield traits of ten Egyptian barley cultivars. It employs statistical analyses and biplot graphs to interpret the correlations among the traits. Furthermore, the study examines the performance of barley genotypes and their resistance to the disease. The findings suggest that the GT biplot analysis is valuable for this study.