Abstract: Fresh mushrooms (Agaricus bisporus) were placed in jars linked by continous flow (100 mL/min) of humidified air (control), 40%, 60%, 80% or 100% O2 at 2℃ for 12 days to investigate the effects of high oxygen atmosphere on quality and resistant substance. The results showed that the content of soluble solids was slightly affected by high oxygen concentration. The treatments with 60%-100% O2 significantly inhibited the decrease of firmness, browning and increase of cell membrane permeability of mushroom. The content of free proline under 60%-100% O2 was lower than that of control, and the difference was significant (p<0.05). The content of soluble protein under 60%-100% O2 was higher, and there was no significant difference. So high oxygen concentration is effective on improving the quality of mushroom.