A simplified method is proposed to obtain liquefaction-induced residual displacement. This method involves four procedures. First, the state of stress before an earthquake is calculated by an analysis considering the deposition and construction process of the ground. Next, the resistance factor against soil liquefaction, FL, is evaluated by a simplified liquefaction analysis. Then, post-liquefaction stress-strain relationships are evaluated from FL and liquefaction strength, RL. Finally, the difference between the initial stress and the stress evaluated by the post-liquefaction stress-strain relationships is applied as an external load (driving force) to a soil-structure model. A sequential laboratory test was conducted in order to obtain post-liquefaction stress-strain relationships, and these relationships were expressed as a function of RL and FL. Moreover, a stress-strain model for unliquefied layers, which is also important in evaluating liquefaction-induced flow, is proposed; it is an elastic-perfectly plastic model based on Mohr-coulomb and Dracker-Prager failure criteria. Two case histories showed that the simulated results agreed with actual earthquake damage.