The quality detection of concrete cutoff wall of Junmin Reservoir dam in Poyang County adopted nano transient electromagnetic method.It has good detction effect,provides the reliable scientific basis and laid a solid foundation for project acceptance check and management work.This method has the merits such as a big detection depth,small volume effect,high work efficiency,high vertical resolution ratio,small effects of terrain,intutive and clear image.It can provide references and promotion for similar projects.