A modified two - dimensional dynamic effective stress method is established and also the corresponding program presented in the paper . and the method is used for analyzing the effects of liquefaction of sand soil zone on surface ground motion and the response spectrum of acceleration 、 velocity and displacement 本文在現有研究的基礎上,建立了一種土體二維有效應力動力分析方法并編制了相應程序,并以此計算分析了飽和液化砂層對地表加速度反應譜、速度反應譜、位移反應譜的影響。