Abstract: To evaluate the rainfall erosivity quantificationally as accurate as possible, subsequently to estimate the potential capacity of rainfall-induced soil erosion, daily precipitation data was collected from 96 meteorological stations of every county in He-Long section of the middle reaches of Yellow River during 1981 -2010. Based on the rainfall erosivity model of half month, the spatio-temporal variations of rainfall erosivity at half month, month, season and year scale were analyzed. Results indicated that: 1) Rainfall erosivity at the second half of July, August, and summer were greatest at the corresponding time scales.Average annual rainfall erosivity increased from northwest to southeast at space. 2) Annual rainfall erosivity showed decreasing trend overall, and the area of rainfall erosivity reduced occupies 68.45% of the whole area. In addition, the rainfall erosivity reduced in the first half of July made the largest contribution to the decrease of the annual rainfall erosivity. 3) The increasing area of annual rainfall erosivity mainly located at the northwest and southeast of the He-Long region, moreover, rainfall erosivity in the first half of July showing increasing trend only covered 1.12% of the total area.