A new ocotillol-type saponin (PGQ) has been semisynthesised from 20(S)-ginsenoside Rg3 for the first time, in with a yield of 73%, by oxidation and cyclisation of the side-chain. Its structure was characterised by IR, HR-MS, (1)H NMR, (13)C NMR, (1)H-(1)H COSY, DEPT, HMBC and HMQC spectroscopy as 3-O-[beta-D-glucopyranosyl-(1-2)-beta-D-glucopyranosyl]-dammar- 20S,24S-epoxy-3beta,12beta,25-triol (1). The saponin produced a beneficial effect on resuscitation of haemorrhagic shock as follows: first, it could significantly rise increased mean arterial pressure; second, it could increased blood oxygen content; third, it could markedly decreased serum lipoperoxidase and increased superoxide dismutase (SOD) activities. Thus, the saponin had the effect of an anti-haemorrhagic shock.