Limiting flux during the ultrafiltration of citrus pectin was investigated. The gel layer by concentration polarization is responsible for the limiting flux of the ultrafiltration of pectin.The limiting flux can be modeled using Michaelsgel layer equation taking Cg=20.70　g/L of pectin, and this value is independent of fluids turbulence near the membrane surface and the type of membrane. As far as a certain concentration of pectin is concerned, Jlim∝ω045; therefore, the more turbulent the fluid near the membrane surface, the greater the limiting flux and the type of membrane has no effect on the limiting flux. A correlation for mass transfer coefficient has been developed under turbulentflow.