Since 2010, the Chinese sturgeon Acipenser sinensis, one of the first-class national protected animals in China, has been classified as Critically Endangered in the IUCN Red List of Threatened Species. The last spawning ground of the Chinese sturgeon is located just downstream from the Gezhouba dam(GZD) after its construction, and thus, it is critical to retain the availability of the spawning ground for the sustainability of the species. The riverbed substrate and its surrounding microhabitat supply an environment for survival and development of the embryos of the Chinese sturgeon, and so chronic change to riverbed characteristics could have significant consequences on the reproductive success of the Chinese sturgeon. Based on long-term investigation of the ecological factors linked with natural spawning and especially observation of the spawning substrate characteristics over the last 8 years, the arrangement and structure of the bottom substrate of the spawning ground have been greatly changed from impounding of water in the Three Gorge Reservoir (TGR). At the same time, the critically important spawning sites as well as the spawning scale have also changed with spawning events occurring at spawning sites downstream (SSD) from 2004 to 2007 and spawning sites upstream (SSU) from 2008 to 2012. The ecological effects of the bottom substrate on spawning success and embryo development of the Chinese sturgeon are still not well documented. To study the effects of bottom substrate characteristics linked to impounding of water in the TGR, acoustic surveys with a scientific echo-sounder (2004-2012) and underwater video surveys (2007-2012) were conducted in the 6 km reaches of the Yangtze river just downstream from GZD including the last spawning ground of the Chinese sturgeon. The echo-sounder surveys showed that great changes in bottom hardness (as seen in the 1^st part of the 1^st Bottom Echo from start to peak of the echogram) and roughness (as seen in the 2^nd part of the 1^st Bottom Echo from the peak to the end of the echogram) have occurred in the spawning ground. Even though bottom hardness did not change significantly over the whole spawning ground (P > 0.05), bottom hardness in the SSD in 2012 was significantly higher than that in 2008 and 2004 (P < 0.05), while at same time, bottom hardness in the SSU in 2008 and 2012 was significantly lower than in 2004 (P < 0.05). Bottom roughness over the whole spawning ground and in the SSD increased significantly from 2004 to 2012 (P < 0.05), while no significant changes were found in the SSU.Underwater video surveys showed that with the erosion by the cleaner water impounded in the TGR, the coarse and fine sand that could be observed in the spawning ground in 2008 had almost completely disappeared in 2012 and the embeddedness (a term describing the degree to which river bottom gravel, cobbles and boulders were covered or had settled into the coarse and fine sand of the river bottom as obervered from the underwater video surveys) in the whole study area had decreased dramatically (P < 0.05). The embeddedness in the SSD and SSU was about the same in 2008 and 2012, respectively. Particular note was that the embeddedness in the SSD from 2007 to 2012 was almost zero, which meant there was no coarse or fine sand embedded on the bottom and this represented a significantly lower embeddedness than that in the SSU in 2008 and 2012.Combining the changes in riverbed characteristics with the displacement of the critical spawning site of the Chinese sturgeon, we found that where spawning occurred was in areas with moderate bottom hardness, roughness and embeddedness. We can conclude that the changes in riverbed characteristics have possibly caused the positional changes of the critical spawning sites of Chinese sturgeon. The changes in bottom characteristics of the spawning ground may have also caused a degradation in suitability of the bottom substrate for spawning and consequently may have contributed to the habitat loss of the spawning ground. However, further proof is required in future studies, which will thoroughly evaluate the ecological effects of the erosion by the clean water from the TGR and help for outline the necessary steps to be taken to rehabilitate the spawning ground of the Chinese sturgeon.