In order to further study the vertical velocity profile with suspended sediment in open channel, a series of experiments are conducted in a flume. The time average velocity profiles are analyzed by the measured time average velocity data, and compared with the results obtained from modified logarithmic law for the vertical profile of open channel flow. The results indicate that the time - averaged velocity profile accords with that obtained by the modified logarithmic law, that the Karman constant K in the center of the flume is less than that near the wall of the flume, and that, however, the Karman constant decreases with the increase of sediment concentration.The study of this paper can deepen the recognition of vertical distribution in open channel flow.