Abstract: Topographical variation analysis is an important method and approach in studying neotectonics and paleoearthquakes. Recently, we discover a line-type shallow canyon developing on inner continental shelf plain beside the Nan'ao Island of east Guangdong Province. This shallow canyon,adjacent to the Bin-hai Fault Belt of South China Sea,could not have been formed by exogenic force erosion, but by surficial deformation of the earthquake fault. This discovery will give some suggestions and speculations about fur-ther researches on activity of the east segment of the Binhai Fault of South China Sea and on seismic activity in east Guangdong Province and Taiwan Strait.