Abstract: The physical and chemical properties of the permeate fluid and retentate fluid obtained by step-bystep ultrafiltration were studied in this paper. Results showed that under the same protein concentration condition 10ku permeate fluid and 5ku retentate fluid had relatively poor thermal stability, and 3ku retentate and 1ku retentate had good thermal stability, 5ku, 3ku and 1ku permeate fluid had the best thermal stability. Color values of all permeate and retentate fluid increased along with the increase of staying duration, and the clarity decreased. The permeate fluid of ultrafiltration membrane with different molecular weight cut-off had different taste characteristics, 5ku permeate fluid had the strongest bitter taste, while 1ku permeate fluid had the weakest bitter taste. 3ku permeate fluid had the strongest fresh taste, while 1ku permeate fluid had the strongest sweet taste. 3ku permeate fluid contained the largest amount of total sugar, while 10, 1ku permeate fluid ranked second, and 5ku permeate fluid contained the least amount of total sugar. All levels of ultrafiltration had little cut-off effect on Zn ion, the membrane of 5ku retentate had the largest cut-off amount for Na, Mg and K ions.