Caldesia grandis Samuelsson is an endangered wetland herb on the brink of extinction in the vast area of Mainland China, which holds close to one eighth of the world''s vascular plant species. The pollination ecology and breeding system of C. grandis were investigated from three natural populations occurring in two wetlands near the top of Mangshan Mountain in central China. Propagation is achieved through turions, which commonly occur in the inflorescences. Flies (Insecta; Diptera) were the most frequent visitors to the flowers of C. grandis; however, bees composed a larger proportion of effective pollinators. Existence analysis revealed a peak of mortality density in mid-May corresponding to an environmental sieve in the period following the establishment of plantlets. An updated diagnostic of the conservation status of C. grandis in China was formulated. The main threats to this species are catastrophic events, especially human impact activities (agriculture, hobbyists'' collections, and infrastructure construction). Establishment of a monitoring program is proposed, and both in-situ and ex-situ strategies are recommended for effective conservation of C. grandis.