Abstract: An experiment was conducted to investigate the treatment of soybean whey with a dual-step ultrafiltration system which consisted of an air blasting enhanced vibratory ultrafiltration (MWCO50kDa) and a cross-flow ultrafiltration (MWCO10kDa). The results revealed that the operation duration of each cycle in the treatment of soybean whey with the dual-step ultrafiltration system reached more than 23h. The protein concentration of soybean whey was reduced from 0.5% to 0.04%; and both total sugar and salinity were retained at a lowered rate of about 10%. The membrane permeate flux of the fouled system was restored to more than 90% by chemical cleaning in 2h. The separation property of the membranes adopted in the system was not changed remarkably during long-term operation. The whey protein obtained in the experiment was a satisfactory product in that the protein concentration was higher than 70% and the salinity was around 10%.