The invention provides an L-tryptophane fermentation process. The fermentation process comprises the following steps: adding 2g cottonseed cake powder to every 1 liter of an L-tryptophane fermentation medium to carry out fermentation; carrying out circulating filtration in the fermentation course when the yield of acetic acid is more than 5g/L and allowing clear fermentation liquid obtained after separation to enter into an extraction procedure; allowing concentrated bacteria liquid obtained after extraction to enter a fermentation tank, then replenishing a dialysis medium and then carrying out fermentation further, thus obtaining L-tryptophane. By adopting the fermentation process, the L-tryptophane production cycle is lengthened by 20 hours, the acetic acid concentration is maintained below 5g/L, the single tank yield is increased by 89% or above, and the conversion rate is increased from 17.0% to more than 18.5%; as the cottonseed cake powder is added to the fermentation medium and the cottonseed cake powder which is not utilized by thalli plays a role of a filter aid during filtration, the fermentation liquid filtering rate is increased from 85mL/min to 183mL/min.