The effects of mild pressure(1MPa) and holding time on the membrane permeability of Saccharomyces cerevisiae CICC1447,CICC1339 were determined with CO 2 and N 2 as the pressure media.The results showed that the conductivity of the cell suspension,the OD 260 and OD 280 of the supernatant increased with the pressure increase,which indicated that the cell leakage aggravated with the pressure increase and the membrane permeability increased with the influence of mild pressure.The cells were treated with mild pressure(1MPa) with N 2 as the pressure media,and the holding time is 1h and 3h respectively.Fluorescence intensity generated by PI and DNA was identified.The results indicated that the fluorescence intensity of CICC1447 improved by 6% and 13.56% compared to normal.And the fluorescence intensity of CICC1339 improved by 3% and 7%.So the further conclusion was made that mild pressure could increase the permeability of cell membrane of S.cerevisiae.