Abstract: The first-stage storage of the Three Gorges Project started on 1 of June 2003 and ended on 10 of June of the year. In order to investigate the influences of the Three Gorges Project(TGP) on the Yangtze River estuary and adjacent area environment, a cruise was carried out to synthetically study the environment from 15 to 25 of June 2003. In this paper, form characteristics and substance constituents of suspended matters in different waters are discussed based on micro-examination and X-ray diffraction of suspended matter samples. Study results show that the form characteristics of suspended matters vary largely from Xuliujing to Yangtze River estuary adjacent area. Most of suspended matters are single particles from Xuliujing to the south branch, while there are many flocculent particles near the river mouth bar, where exists the turbidity maximum. The flocculent particles are characteristic of agglomerates, big agglomerates and reticulate agglomerates. In the Yangtze River estuary adjacent area, some suspended matters are single particles, and others are organic agglomerates. Most of suspended mineral particles are granulose and platy. Suspended mineral particles are composed of detrital mineral, such as quartz and feldspar, and clay mineral. From riverway to Yangtze River estuary adjacent area, the contents of quartz and feldspar decrease, the contents of illite and chlorite increase and the content of kaolinite first decreases and then increases. Generally, the morphologic features and substance constituents of suspended matters in the estuary and adjacent areas after the TGP storage showed no significant changes compared to those before the storage, although the number of small flocculent particles at Xuliujing increased after the TGP storage.