The invention provides a crystallization process for extracting L-tryptophan from fermentation broth. The crystallization process comprises the following steps: continuously applying 50W ultrasound to crystallize concentrated fermentation broth at the temperature of 4 DEG C after the fermentation broth is treated by heating inactivation, microfiltration, ultrafiltration and rotary evaporation, wherein the ultrasound action time is 15-20min, so that tryptophan concentrated solution is quickly developed into minute crystals with uniform size from original crystal nucleuses with different sizes under the ultrasonic cavitation; then, allowing standing still for 1h at constant temperature of 4 DEG C, performing suction filtration on obtained suspension, and drying, so as to obtain a finished product. The parameters of crystallization rate, the conductivity change rate, the product yield, quality and purity and the like of the crystallization process and the existing common crystallization process are compared. The crystallization process provided by the invention mainly aims at solving the problems of multi-times of crystallization, long crystallization period, bigger crystals, non-uniform size, undesirable crystallizing quantity and the like existing in the traditional tryptophan extraction process, therefore, the crystallization rate is improved, the crystallization period is shortened, the L-tryptophan product yield is improved, and the purity is not influenced.