The Elymus grasses, known for their strong ecological adaptability, are a primary genetic resource for improving the quality of grasslands in the Qinghai-Tibet Plateau. This study focuses on the diversity of inflorescence branching types among Elymus species in alpine regions. It examines 76 Elymus inflorescence branching germplasm resources from different areas of the Qinghai-Tibet Plateau, measuring and analyzing the related phenotypic characteristics. The findings are as follows: There is significant variation among the 76 materials, with a high diversity index across 29 traits, averaging an H' index of 5.19. In this survey, Elymus inflorescences showed only primary branching, averaging 7.03 branches per inflorescence, with a mean branching rate of 33.90%. Branches typically occur in the middle to lower part of the main inflorescence axis, with the highest variation (98.14%) in the starting point of branching on the axis. Correlation analysis revealed significant positive correlations between the number of branches and branch rate, branch width, total length of branched spike, and total length of inflorescence. Branch rate was highly correlated with branch width and the endpoint of the branch. The total length of the branched spike was significantly correlated with the total length of the inflorescence and the number of seeds on the branched spike. Principal component analysis identified 4 main components, accounting for 84% of the cumulative contribution rate. The first principal component (36%)—largely characterized by the number of branches, branch rate, branch width, and total length of branched spike—reflects the variability related to the quantity and length of branches. The second principal component (30%) is characterized by total seed weight, branched spike seed weight, main axis seed weight, and total inflorescence weight, reflecting seed weight and distribution characteristics. The third principal component (12%) is dominated by characteristics like the starting and ending points of branches, the length of the main inflorescence axis, and seed number linear density, reflecting variations in branch occurrence sites and overall inflorescence length. Cluster and phylogenetic relationships analysis based on inflorescence phenotypic characteristics categorized the 76 Elymus inflorescence branching germplasm resources into nine types: high branching, dense branching, long sparse branching, balanced branching, heavy-seeded high-yielding, medium branching, sparse branching, short low-yielding, and uniformly stable-yielding. These nine categories primarily reflect the characteristics of branching and seed yield, providing a basis for further selection of ideal inflorescence types. In summary, the 76 Elymus inflorescence branching germplasm resources show high diversity and phenotypic variation. The occurrence of branching alters the pattern of seed yield, providing a theoretical foundation for improving seed yield of Elymus grasses in alpine regions.