In order to evaluate the relationship between dispersion and ultrasonic time, dynamic light scattering experiment was carried out on both 0.20 g/L xyloglucan solution and 0.20 g/L β-galactosidase-degraded xyloglucan solution with different time intervals. Data showed that the variation trends of particle size in xyloglucan and enzyme-degraded xyloglucan solution were similar: decreased first and then increased with the incremental time. Thus, there should be an optimum time interval during which the smallest particle size can be obtained if experimental conditions were excluded in theoretically. In addition, the optimum time interval varies in different polysaccharides since it may be associated with molecular conformation, based on the results of our work. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40973.