Determination of the distinctness, uniformity and stability (DUS) of plant varieties is an important means of protecting the original innovations of breeders, increasing the enthusiasm of breeders and promoting the development of plant breeding. In this study, combinations of SSR markers and DUS morphological characteristics were used to identify varieties. The genetic diversity of 30 flax plant varieties was analyzed using 20 SSR markers and 18 DUS morphological characteristics. The results of the morphological characteristic analysis showed that the 30 flax varieties had high genetic diversity. Ninety allelic variations were detected in 20 polymorphic SSR molecular markers, and 2 ~ 10 allelic variations were detected in each pair of primers. The diversity index (H) of Nei’s gene was 0.10 ~ 0.39, with a mean value of 0.23; the Shannon information index (I) was 0.19 ~ 0.57, with a mean value of 0.37; and the polymorphism information content (PIC) was 0.25 ~ 0.82, with a mean value of 0.51. Cluster analysis revealed that there were correlations between the SSR markers and morphological characteristics, and there were also some differences. These results show that these two methods have good potential for future research, especially for DUS analysis of hundreds of varieties. Therefore, the use of molecular markers can reduce the cost and duration of resource consumption, and more importantly, identify and protect highly specific plant varieties.