The endangered and rare species Urophysa rockii belongs to a unique genus of seed plants that is only distributed in the Jiangyou area of Sichuan, China. Breeding system characteristics and flowering phenology are the most important factors influencing plant reproductive success. The flowering phenology, floral characteristics, and breeding system characteristics of U. rockii were investigated in Jiangyou, Sichuan. Analysis showed that:1) It is a bisexual flower with an umbel and a long flowering period. It lasted from December to April of the following year. The flowering period of one flower was 8 to 15 days, and the flowering period lasted for about 4 months. 2) The flower of Urophysa rockii showed no pollen activity before the flower was opened. On the first, second, third, and fourth day of anther dehiscence, pollen activity was 94.8%, 90.3%, 81.6%, and 62.9%, respectively, and pollen viability obviously decreased. Stigma receptivity began the third day after pollen scatter, and reached the highest levels on the fourth and fifth day, then the eighth day after pollen scatter, stigma receptivity was lost. Stigma receptivity and pollen viability overlapped for about 5 days. 3) The pollen-ovule ratio was 938.5±250, according to the Cruden standard and the sexual reproduction system was facultative outcrossing. 4) According to the standard of Dafni (1992), the OCI=4, showing that the breeding system was out-crossing, partly self-compatible, and insect pollinator-dependent. 5) The seed setting rate of palmification was above 80.0%, slightly higher than the natural seed setting rate of 78.9%. Direct bagged seed setting rate was 5.71%; emasculation by bagging and removing pistil bagging were mostly infertile. The results showed that in the breeding system of this species, out-crossing was predominant, partially self-compatible, and there was no apomixis, but it required pollinators. The floral characteristics, flowering phenology, and breeding system of Urophysa rockii provided some reproductive assurance and evolutionary potential for its ability to adapt to the special environment. The aim of this article was to provide the theoretical basis for the ex-situ conservation and rejuvenation of population reproduction of Urophysa rockii.