Abstract: Based on the summarization of research on total dissolved gas(TDG)supersaturation,field observation of TDG downstream of Zipingpu dam was taken. The dissolved gas saturation levels were measured and recorded along transects distributing in 40 kilometers downstream of the Zipingpu dam. It shows that the depth and sand concentration of the river is an important factor affecting the desorption of TDG downstream of high dam. It provide a basis to find out the rule of desorption of dissolved gas supersaturation downstream of high dam,which is important for protecting fish in downstream of high dam.