The Chongming Dongtan Nature Reserve, one of the largest nature reserves for migratory birds in East Asia, is located on Chongming Island at the mouth of the Yangtze River. Since Spartina alterniflora was introduced into the Chongming Dongtan Nature Reserve in 1995, there has been a rapid expansion of this species, seriously threatening the overall biodiversity. The exotic plant S. alterniflora has expanded rapidly and formed a large area of mono-dominant community at Chongming Dongtan by its fast sexual reproduction and asexual propagation. Previous studies on the salt marshes at the Yangtze Estuary reported that S. aterniflora had a great capability of asexual propagation and the range expansion rate was three to five times faster than that of native species Phragmites australis. However, the sexual reproduction and its role played on the spreading of S. aterniflora at the Yangtze Estuary were still unclear. In this study, the seed production and germination response of S. alterniflora seeds to temperature were investigated at the Chongming Dongtan nature reserve. Three sampling sites, lower intertidal zone (LIT), middle intertidal zone (MIT) and higher intertidal zone (HIT) , were set along an intertidal gradient at the northern part of the nature reserve, stretching from the 1998 inland dyke and moving towards the low tide. During November 2008, the total number of S. alterniflora culms and fruiting culms were recorded at each of the five 1 ? 1m plots set randomly at the sampling sites of LIT, MIT and HIT. And the seeds collected from the sampling sites were taken to laboratory for chilling treatments and germination experiments in climate chambers. The results showed that along an intertidal gradient, the middle intertidal zone (MIT) had the largest seed production of 44523/m2, followed by the higher intertidal zone (HIT) of 31150/m2 and the lower intertidal zone (LIT) of 17250/m2. The variation in seed production and viability of S. alterniflora at the Chongming Dongtan Nature Reserve was strongly correlated with the intertidal gradient. The middle intertidal zone at an elevation of 2.9—3.5 m was the favorite habitat for S. alterniflora where it had the higher number and better quality of seeds. While the ebb and flow at the lower intertidal zone and the intense competition with other species such as P. australis at the high intertidal zone could be responsible for the reduction in seed production and seed quality. The seeds of S. alterniflora from all intertidal zones could germinate at a temperature range of 10 to 30℃ and showed a trend of increase followed by decrease in germination percentage and germination speed. Seed germination percentage reached the highest and germination speed was the fastest under the treatments of 25℃constant temperature and 20/30℃alternate temperature. Moreover, the germination percentage was higher under an alternate temperature than that under a constant temperature with the same cumulative temperature. The results indicated that the middle intertidal zone (MIT) could provide an important source while the temperature in April and May could promote the seed germination for the fast sexual spreading. The results from this study could provide useful insights into the population ecology and the control of this invasive plant at the nature reserve.