Abstract: Seeds and seedlings of rape cv. Yuhuang No.1 were treated with 25 %PEG-6000 in combination with different concentrations (5 and 25 m mol/L) of trehalose (TH) and control to study the influence of external TH on rapeseed germination and seedlings growth and physiology under the osmotic stress. The results showed that 25 m mol/L TH could promote germination of rapeseed and seedlings growth under the osmotic stress, and the germination rate increased by 19.52%, the germination index increased by 33.12% and the vigor index increased by 1.76 times. At the same time, 25 m mol/L TH alleviated the accumulation of MDA by 37.77 % and accelerated the accumulation of proline by 6.96 %, and significantly enhanced the activity of peroxidase (POD) by 33.11%, superoxide dismutase (SOD) by 1.4 times and catalase (CAT) by 51.08 %. In comparison with these changes, the effects of lower concentration of TH (5 m mol/L) and corresponding control were not so obvious. The above results indicate that higher concentration of TH (25 m mol/L) could promote the germination of rapeseed and the seedlings growth under the osmotic stress.