A due considerations have been paid to the characteristic features and phenomena of the tremendous loess landslides in crows induced by irrigated water. All of them occurred along Heifangtai edges of platform,Gansu province,China. Based on these features and phenomena,such as large extents,high-speed and long traveling distances,their mechanism,kinematical approach and slope stability are analyzed. The regional prevention rules are presented that to take drainage work as the dominant factor and the simple engineering prevention the second one.