To further investigate the effects of operational conditions Oil Ultrafiltration membrane fouling, ail experiment using Kraft pulp liquor diluted with well water as synthetic raw water was carried Out to examine the influence of raw water concentration, permeability, cross-flow velocity, backwash mode, interval, and backwash pressure on transmembrane pressure (TMP) and permeated quality by applying all Ultrafiltration membrane with the molecular Weight cut-off (MWCO) of 150 kDa. The results Show that the raw water UV254 value of 0.03-0.16 call cause few changes in the transmembrane pressure and the operating efficiency can be increased when UV254 value is greater than 0.35, ail irreversible fouling of the Ultrafiltration membrane may be observed. Oil the principle of no influence exerted oil the transmembrane pressure, the increase of the membrane Surface velocity may result in water permeation, while membrane cleaning, that is, at cross-flow velocity of 1.6 m/s, few changes are observed in the transmembrane pressure. Although the backwash intervals and pressure have effects oil the transmembrane pressure, the backwash period is not an important factor influencing the transmembrane pressure. The permeated water quality indicates that the membrane fouling layer plays the same filtration function as the membrane itself.