Abstract: A method for the removal of salts in alkaline corncob xylan solution by tangential flow ultrafitration was presented in the paper. By comparition of the permeate flux, the overall removal coefficients of salts and the retention ratio of xylan of different regenerated cellulose membrances whose nominal molecular weight cut off were 10000,5000and 1000 at the same operating condition, a suitable nominal molecular weight cut off ultrafiltration membrance was chosen. The effect of operating pressure, temperature, alkali extraction concentration and flow rate on the permeate flux were investigated, and the suitable technical parameters were therefore determined.