The effects of oxygen concentration on storage quality of Agaricus bisporus were studied at 3℃ and 95% relative humidity under controlled atmosphere storage. The results show that 5% oxygen concentration inhibits the respiration and postpones the arrival of respiratory climacteric of mushroom. Weight losing rate, browning degree and firmness of Agaricus bisporus all decreases with the reduction of oxygen concentration. The soluble solid of mushroom is maintained and the ripening is delayed with the low oxygen concentration.