Abstract: Ground instability, calculated seismic settlement values and isolation function of a liquefied soil layer are analyzed herein. The relationship between liquefaction index, ground failure, isolation function of a liquefied soil layer, and earthguake damage of multistoried buildings are also studied in this papar. The classes of liquefaction hazards are determined according to the double function principle of liquefied soil, and methods for assessment of seismic liquefaction hazards at construction sites are suggested.