Abstract: Collapsible loess and loessial soils are unsaturated and underconsolidated, having macro pores and vertical fissures. At its natural water content, its compressibility is rather low and its strength is somewhat high. But, upon wetting its strength will decrease significantly, and then it will collapse either under its own weight with no surcharge or under surcharge load and cause damage to buildings and structures. Therefore, it is very important to assess correctly the collapsibility of the loess foundations in collapsible loess regions and take appropriate counter measures to ensure both safety and economy.