Abstract: Primary root length， lateral root number， root/shoot ratio and chlorophyll concent were important drought resistance indexes of plant seedlings. In order to investigate the effect of Ar+ implantation on drought resistance of soybean seedlings， different doses of Ar+, 0, 500, 1 000, 1 500, 2 000, 2 500, 3 000, 3 500, 4 000×26×103 ions·cm-2, were injected into the seeds of soybean under the ions bean erengy of 25 keV. The results indicated that 1 500×20×1013 ions·cm-2 of Ar+ beam implanting could promote primary root elongation， increase lateral root number and root/shoot ratio， and improve chlorophyll content, proline content and peroxidase （POD） activity of soybean seedlings.

Key words: Ar+ ion implantation, soybean, drought resistance