Stipagrostis species are among grasses that are grown mainly in arid areas particularly on moving sand dunes. Several species of the genus are useful in sand dune fixation as well as pasture values. In order to investigate genetic variation by karyotypic characteristics, 4 populations of the genus were studied in this research. To achieve the goals, karyotypic characteristics such as short and long arm length and total length of the chromosomes of the populations were measured. Ratios of the short arms to long arm and long arm to short arm of the chromosomes were also calculated. Principal components analysis was performed on the data to classify the populations based on the first two components of the analysis. The first two principal components were plotted to get scatter plot of the populations. Results of the analysis were used to study the role of the chromosome traits on principal components. Studies showed that the role of chomosome total length, long arms length, and long arms to short arms length ratio with values of 2.20, 0.71 and 0.82 respectively, showed the most effective role in formation of the first principal component. All plot showed that Mashhad population is in a far distance to other populations.