Using the observation data of fluid mud after three huge stormy waves in the Yangtze estuary, we analyze the development, transportation and dissipation process of the fluid mud in 12.5-meter deepwater channel The results show that the fluid mud in the channel develops clearly after huge stormy waves in the flood season. Its maximum thickness can reach about 3.5 to 3.8 meters and the volume can reach about 27 million cubic meters. The scale of fluid mud’s development relates to the duration of stormy waves and the tidal regime during stormy waves. The longer the stormy waves continue, the larger the fluid mud develops. And when the stormy waves meet the spring tide, the large-scale fluid mud can be formed; When the stormy waves meet the neap tide, the scale of fluid mud is smaller relatively. Fluid mud mainly develops in 12.5-meter channel, and there is little fluid mud on the riverbed of both sides of the channel. After the fluid mud is formed, it will move up and down in the channel under the effect of tidal current, with an amplitude of fluctuation about 13~18 kilometers. The fluid mud formed in the spring tide will migrate upward as a whole during the following neap tide. Fluid mud in deepwater channel exits about 5~10 days, and the dissipation of fluid mud is mainly connected with the enhancement of tide power. The fluid mud formed after stormy waves will disappear gradually with the subsequent spring tides.