In this paper,the seismic damage phenomena in the loess in Yongdeng M_S5.8 earthquake region,Gansu province are collected and analyzed.The damages are divided into two types,one is crisp crash by the quake on the top of the hill,the other is small-scale landslide.For the loess samples from the intensity areas of Ⅶ,Ⅷ degrees,the quantitative analysis on the SEM pictures and the common geo-engineering experiments are carried out.The results show that the loess from this region is full of big pores and is prone to seismic damage when the damp ratio becomes higher.Combining the general knowledge of the field investigation with the indoors experiments data and noticing that just before the earthquake there was a storm,we impute the loess damage to water penetrating on the slope surface and eroding in the slope foot.According to the above analysis,the mechanisms of the two kinds of seismic damage are proposed.