Abstract: To obtain new ryegrass germplasm with enhanced drought and heat tolerance a genetic transformation experiment using plants from the genus Lolium was conducted. By using mature seeds of ryegrass as explants and adoption of the overexpression vector,tissue culture and regeneration system of ryegrass, and genetic transformation mediated by Agrobacterium tumefaciens, the S-adenosylmethionine decarboxylase gene cloned from Festuca arundinacea (FaSAMDC) was introduced into the genome of ‘Tetragold' annual ryegrass and ‘Four Seasons' perennial ryegrass. Eighty-nine transgenic plants (45 Tetragold and 44 Four Seasons) were regenerated from independent resistant calli, which were confirmed by antibiotic resistance screening, PCR assay and southern hybridization analysis; the transgenic frequency was 2.93% and 2.28%, respectively. Drought and heat resistant tests under high temperature (30 ℃) and moderate drought stress showed that in Tetragold, the root to shoot ratio was 7.1% higher, leaf relative water content (RWC) 13.1% higher and the RWC descent scope 5.5% lower than the controls; for transgenic Four Seasons plants the root to shoot ratio was 6.5% higher, RWC 12.5% higher and the RWC descent scope 6.5% lower than the control; differences between transgenic plants and controls were all statistically significant (P<0.05), indicating that drought and heat resistance in transgenic plants was significantly improved. Observations of morphological and growth characteristics showed that, compared with non-transgenic plants, leaf length, plant height and main stalk pitch number of transgenic plants were lower but leaf width and tiller number per plant were higher. Leaves of transgenic plants were darker in colour and plants tended to become compact with tufted leaves suggesting that the inserted FaSAMDC gene was involved in the regulation of physiological function, such as gene expression and cell division. The transgenic material developed in the study could be used as foundation for the cultivation of new ryegrass varieties with enhanced drought and heat resistance.