Abstract: L- lysine production by Corynebacterium glutamicum with optimized medium through continuous fermentation was studied in 5L fermenters.Under the same conditions, bacterial biomass in optimized medium and original medium were respectively 8.0g /L and 9.3g /L, and the maximum production rate were 0.53 g /L /h and0.72 g /L /h respectively.After 48 hours' fermentation, L- lysine concentration, L- lysine yield and conversion ratio were respectively 20.8g /100 mL, 588.2g and 0.713 g /g for the optimized medium, which increased by 6.1%, 2.3%and 12.2% respectively compared with the original medium. Optimized medium significantly decreased the raw material consumption and increased the conversion efficiency of L-lysine production.