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In order to study the morphological diversity of Hibiscus syriacus cultivars and their relationships, we observed morphological characteristics and exine sculpture of 22 H. syriacus pollen grains by scanning electron microscope, and used R-type cluster analysis and principal component analysis to extract appropriate indicators for UPGMA cluster analysis. The results were as follows:(1)The pollen of H. syriacus was single-spherical, nearly spherical with diameter of 148.98-111.65 μm with thorn-like ornamentation on the surface with length of 27.42-14.79 μm; The tip of the thorn was sharp, and the thorns distributed around scattered pores; The pollen surface was distributed with granular protrusions and the apertures were irregular.(2)UPGMA cluster analysis was performed after extracting principal components of the measured indicators. When the Euclidean mean distance threshold was 6, 22 H. syriacus cultivars were divided into six categories. The single-petal blue-violet cultivars 'Bluebird', 'Dan Ban Zi Fen' and 'Xi Ye' had close relationships, and semidouble cultivars 'Lavender Chiffon' and 'China Chiffon', 'Pink Chiffon' had close relationships, while white single-petal 'Wood Bridge' and 'Hamabo' were relatively close. It was believed that the single-petal blue-violet cultivars in H. syriacus were more primitive than the pink and white semidouble cultivars, while purple semidouble cultivars were more evolved and the white single-petal cultivars were highly evolved. The results of this study provide theoretical basis for genetic evolution, taxonomic status, and genetic relationship studies in H. syriacus. [ABSTRACT FROM AUTHOR]