Increasing evidence indicates that hydrogen sulfide (H₂S) is the third ‘‘gas signal molecule’’ after NO and CO in animal. In the present study, we found that soybean (Glycine max L.) seedlings sprayed with exogenous H₂S donor NaHS prolonged the longer survival time of life, and enlarged higher biomass of both leaf and root than in non-sprayed controls under continuous drought stress. With the continuous drought stress, the content of chlorophyll in the leaves of both Xu-1 and Xu-6 cultivar of soybean decreased dramatically. The drought-induced decrease in chlorophyll could be alleviated by spraying H₂S donor. It was also shown that spraying with H₂S donor dramatically retained higher activities of superoxide dismutase (SOD, EC 1.1.5.1.1), catalase (CAT, EC1.11.1.6) and lower activity of lipoxygenases (LOX, EC 1.13.11.12), delayed excessive accumulation of malondialdehyde, hydrogen peroxide, and superoxide anion (O₂⁻) compared with the control. These results suggest that H₂S can increase drought tolerance in soybean seedlings by acting as an antioxidant signal molecule for the response.