We studied 1,403 species, 102 families and 473 species of flowering plants in Changbai Mountain Nature Reserve. Based on the data and field investigation, the plant sexual form, life form, flower characteristics, pollination type and fruit type were recorded. The pattern of plant sexual system of flowering plants was inspected, and the relationships between biological and ecological characteristics of flowering plants and plant sexual system were investigated. The results showed that the monoecious, dioecious, and hermaphroditic species accounted for 13.26, 2.13, and 81.61%, respectively. The proportion of hermaphrodites and monoecious plants was higher, and the plant sexual system was related to species richness and phylogeny. Most of the monoecious plants were tree species, and the dioecious plants were mostly trees, shrubs and lianas, and the hermaphroditism was mostly herbaceous plants. The morphological characteristics of flowers were significantly related to the sexual system. The monoecious and dioecious plants were mostly actinomorphic, yellow-green and green-brown small flowers. However, the hermaphroditism flowers were mostly zygomorphic and medium and large sizes with white, blue-purple and pink colors. The dioecious plants were related to generalist entomophily and anemophily, while the hermaphroditism was mainly generalist and specialist entomophily. The plant sexual system was also correlated with plant fruit types. The monoecious and dioecious plants always had dry fruit and the hermaphroditism had fleshy fruit.