in general, three main techniques for polymer degrdation are chemical method, enzymatic method and physical method. whereas, chemical method and enzymatic method usually lead to inwanted monoand oligomers aand to modification of the chemical microstucture of the side groups, and more authors uesed the physical method in recent year. ultrasonic degradation is a great physical method for produceing homologous series of lower molecular weight take place and that the chemical stucture of the polymer is maintained during the degradation process. futhermore, this method is very simple and does not require the addition of reagents, therefore avoids purification process of the degraded sample. the physicochemical property of ultrasonnd treated polysaccharides have been extensively investigated in recent years.