Abstract: Through analysis on the two foundation accidents which took place in China Northwestern area, both the internal and the external factors are found out, the former was the fusible salt content in the foundation soil, the latter was the water permeeting. The permeeting and underground water increased in level, soaked the foundation, and melted the salt and the alike thus resulting in the foundation soil melting and sinking, the foundation settling and wall cracking; The other possible reason why the wall foundation can be damaged was that the level of salt and the alike carried by capillery water, increased and sank into the foundation and the wall, and the sulphate crystal out of it expanded under suitable temperature. The writer points out in the paper that the foundamental measure of treating the foundation of saliferous clay is to prevent water from permeeting into the foundation, prevent water with salt content from permeeting in and out. The defination of the soil should be correct enough in order to guarantee the designers's correct usage of codes/standards, determination of design measures with all factors taken into account, and correct measures of treating the foundation and put an end to such accidents. The loess, the fusible salt content of which exceeds 0. 3%, should be named "Saliferous clay of loess type" so as to describe the engineering characteristics of the soil of this kind in a comprehensive way. There are large areas of saliferous clay in the main three inland basins. It is usually mistaken as a kind of good and natural foundation for its cementation degree, which makes construction companies start their project construction without any foundation treatment, thus causing accidents due to water permeeting. There has not been any codes/standevels, so far, in China for constructions in saliferous clay areas. Concerning organizations are suggested to start working out codes/standards of this kind.