[in Chinese with English abstract:] The powder of Ramalina conduplicans thallus were extracted by petroleum ether (30–60), dichloromethane and ethyl acetate. Six compounds were isolated and identified, they were usnic acid (1), atranorin (2), barbatic acid (3), evernic acid (4), diffractaic acid (5) and salazinic acid (6). They were all for the first time found from Ramalina conduplicans. The antioxidant activity of the six compounds were assessed based on the ability to scavenge DPPH and ABTS free radicals in vitro. The result showed that there was a dosage-dependent effect between DPPH·removal effect and mass concentration of salazinic acid in the test concentration range. In 55μmol/L, the clearance rate of salazinic acid is 57.05%. In 13.75–55μmol/L, there was a dosage-dependent effect between DPPH·removal effect and mass concentration of atranorin, barbatic acid and evernic acid. DPPH·removal ability of usnic acid is better. There was a dosage-dependent effect between ABTS·+ radical scavenging effect and mass concentration of diffractaic acid, salazinic acid and barbatic acid. When the concentration is 55μmol/L, ABTS·+ free radical clearance rate of diffractaic acid is 50.79%, that of salazinic acid is 44.53%, and that of barbatic acid is 44.34%. In 13.75–55μmol/L, there was a dosage-dependent effect between ABTS·+ free radical clearance rate and mass concentration of atranorin. There are benzofuranone, depsides and its derivatives in Ramalina conduplicans, so the lichen can be developed an important source of potential antioxidants. Key words Ramalina conduplicans; compound; antioxidant activity; 2,2-diphenyl-picrylhydrazyl assay (DPPH); 2,2-azinobis-[3-ethybenzothiazoline-6-sulfonic] acid assay (ABTS).