Abstract: Ephemeral gully erosion during rainy season in typical black-soil region is very seriouse. To establish the effective control measures, it is neccessary for analyzing the initiation mechanism of ephemeral gully in the slope land and calculating soil and water losses caused by ephemeral gully. Mechanism of initiation of ephemeral gully during rainy season in the slope land in rolling-hill black soil region of Northeast was analyzed on the basis of three-year field surveys and plots observations. Results show that influx of surface runoff from a certain caused by microtopography relief and unreasonable tillage methods is considered as the main reasons that generate ephemeral gully erosion in rolling-hill black-soil region of Northeast. And connectivity of watercourse caused by silted up furrows in the thaweg can lead to formation of runoff and then give rise to incision directly. And soil loss from their channels is less than that from the sideslopes, so the destructive potential of ephemeral gully is underestimated by measuring its volume of channel only. Therefore, researches on ephemeral gully erosion should be strengthened in future.