To improve membrane performance, the dead-end and Cross-flow ultrafiltration with or without ultrasound irradiation onto the membrane module were carried out using a BSA protein solution. Intermittent or continuous irradiation of ultrasound effectively suppressed the formation of fouling on membrane or removed the fouling layers from membrane. Effect of ultrasound irradiation on the enhancement of ultrafiltration performance was more increased at the operating conditions which form more membrane fouling (at the operating conditions of higher feed concentration and TMP, and lower flow rate). The permeate flukes were enhanced up to 1.9 times in case of the dead-end ultrafiltration and 1.5 times in case of the cross-flow ultrafiltration by ultrasound irradiation onto the membrane module.