A feasibility study on extracting riboflavin from fermentation by spiral-wound membranes with molecular weight cut-offs(MWCO) of 1000 Da,10 kDa and 30 kDa was explored.The membrane with MWCO of 10 kDa was selected to have the best separation effect through comparing the efficiency and flux of the membrane.After the suitable membrane was ascertained,the effects of various parameters for operation such as pressure,flow rate,temperature,concentration factor were studied.The optimal operating conditions were obtained as follows:operation pressure0.2 MPa,operation temperature 30 ℃,flow rate 5 m /s,concentration factor 3.8.The riboflavin purity could reach98.6 % and total recovery rate was up to 97% after ultrafiltration and crystallization