Abstract: Field investigation was performed on the floral syndrome，pollination characteristics，pollinator behaviors and breeding system of Iris tectorum by continuous observations and analyzing data of out-crossing index，pollen-ovule ratio，fruit-set ratio and seed-set ratio. The results were as follows：Under natural conditions，the flowering stage of populations is about 60 days from April to June，and the majority of plants kept blooming in 20th April to 20th May. The flowering stage for individual plant was 10–30 days. The life span of a single flower was about 2 days. The stamen was closed to the lateral side of the petaloid style. The stamen was about 3 mm shorter than the style. The relative position between the stamen and style was always unchanged during the whole flowering stage. It showed that the breeding system was out-crossing，part self-compatibility，insect pollinator-dependent when comparing the results of pollination experiments with the results of out-crossing index and pollen-ovule ratio. The specialized floral structure was suitable for the behavior of the pollinator，Xylocopa appendiculata and Xylocopa tranquebarorum. Hand pollinations improved reproductive success，suggesting that sexual reproduction may be influenced by pollen limitation and less pollinators in nature.

Key words: Iris tectorum, floral syndrome, out-crossing index, pollen-ovule ratio, breeding system, pollen limitation