Abstract: We studied 63 herbaceous peony cultivars and their wild species during 2014-2016. Taking the morphological characteristics of leaf margin and carpel as the main traits of cultivar classification, combining with flower shape and color, we set the classification key of herbaceous peony cultivars, aiming to provide a basis for cultivar identification, application and breeding. We carried out an investigation on morphological characters including the average height and shape of the cultivar, hardness of the stem, the amount of flowers, flower shape, flower color and the carpel hair, stigma and ovary wall color for the cultivar classification. Leaf margin with teeth and carpel hair were used to determine the provenance of the cultivars, and conduct the classification retrieval in combination with the flower shape and color. XTL-850 P stereoscopic microscope was used to observe and picture the leaf margin, carpel, and ovary and stigma color. Color of floral organ was determined by the 6th version of the Royal Horticultural Society Color Chart (RHSCC). Results showed that the 63 cultivars and their wild species all had leaf margin with white transparent bone serration, identified as peony (Paeonia lactiflora) cultivars. The cultivars whose carpel was glabrous or pilose were in the subgroup of P. lactiflora or the subgroup of P. lactiflora var. trichocarpa. In conclusion, 26 cultivars were in the subgroup of P. lactiflora, 35 cultivars were in the subgroup of P. lactiflora var. trichocarpa, and 2 cultivars were in the subgroup of cultivars with carpel petaloid. Taking into consideration of the flower shape and color, and stigma and ovary wall shape and color, we prepared a classification retrieval of the cultivars. Herbaceous peony flowering time varied with years and climate in different areas, but the flowering sequence of early, middle and late cultivars were the same. Herbaceous peony cultivars were in the subgroup of P. lactiflora, P. lactiflora var. trichocarpa, and cultivars with carpel petaloid. Carpel characteristic was the key to identify similar cultivars. The classification based on flower shape and color, and stigma and ovary wall shape and color could be a valuable reference for cultivar assortment, landscape application and new cultivar approval of herbaceous peony. Further study should focus on expanding the scale of herbaceous peony cultivars and systematic analysis of Chinese peony cultivars’ provenance.