Abstract: In order to probe the endangered mechanism of Tetraena mongolica, the pollination ecology of this plant species was studied in the Hang Jiqi Prefecture of Inner Mongolia of China. The results were as follows. The flower morphology was changed with the characteristic of sepals 4～5, petals 4～5, stamens 8～10 and carpel 4～5. Its florescence was from May to the beginning of June with blossoming time of one flower 4～5 days and that of whole tree 8～15 days. The flowers were blooming in the morning and sepal and petal half-open in the afternoon. Before flowering, the filament and style of flowers elongate and the stigma was 2～3 mm higher than the anther. In the time of blooming, the filament was nearly as high as the style, the 4～5 anthers inner stamen crack back, and the secretion was seen in the stigma of the pistil. 4～5 anthers outer stamen crack back one day lately at least. When the flowers wither, all anthers crack back and disperse, and the sepal and petal full close and fall down several days later. The pollen media of Tetraena mongolica Maxim was insects (bees and ants) and the pollination efficiency was low. 50% of stigmas have no pollen, 20% have 1～2 pollens, and only 30% have many pollens. Many pollen tubes were only seen in 25% of stigmas under fluorescentmicroscope. The transformation rate of flowering to fruiting changed from 57.36% to 68.76% and the rate of seed bearing was from 1.26% to 2.80%. Transition rate from flower to fruit was high in the community with worse habitat condition, which was the reproductive strategy of Tetraena mongolica to adapt itself to the hard environment and low fructification rate came from the obstacle in the process of pollination.