Abstract: A field investigation was conducted on the flower structure and breeding system of Zygocactus cv. Danmark red in floral traits， flowering dynamic changes and pollination characters using out\|crossing index， pollen and stigma viability， pollen\|ovule ratio and fruit\|set rate. The main results were as follows: under artificial culture conditions， the population came into bloom from November to December and the population florescence was 64 days. The individual florescence was 34\|53 days， and the florescence of single flower was approximately 6\|8 days. The stamen was close to the lateral side of the petaloid style and 105 cm shorter than the style， and the relative position between the stamen and style was always unchanged in the whole flowering process. The pollen viability of S. truncata was the strongest on the blossom day and the stigma had high stigma acceptability on 3\|5 days after flowering. The out\|crossing index was 4， P/O was about 679， and the breeding system of those species was out\|crossing， self\|incompatibility， insects pollinator\|dependent according to the results of fruit set percentage. The special floral structure and lack of pollinators may be the reasons that those species have a low setting percentage.

Key words: Zygocactus truncata, breeding system, out\|crossing index, pollen\|ovule ratio