A series of factors were examined in the separation of lactic acid (HLa) from lees fermentation by bipolar membrane electrodialysis. When the fermentation with the initial HLa concentration of 13.5 g·L-1 was treated by bipolar membrane electrodialysis under the conditions of voltage 27 V

feeding concentration ratio 1.3

and flow rate 20 L·h-1 for 10 h

HLa concentration of discharging tank was 20.95 g·L-1

which was 1.6 times the initial concentration

a significant concentrated effect. Moreover

the analysis of acid ion migration shows that immigration rate of lactic acid ions is significantly higher than that of other acid ions. The relative separation efficiency of HLa to propionate and acetic acid are lower.