在前人工作的基础上对三层层状介质的瑞利波频散曲线进行了正演模拟研究，对假定的几组典型模型参数的频散曲线进行了认真分析。通过分析可知，各频散曲线之间是互不相交的，从而对此问题有了一个更清晰的认识。指出当低速软弱夹层存在时频散曲线的特点，并根据分析结果，说明”之“字形频散曲线的形成机理。(On the basis of previous work, the Rayleigh wave dispersion curves of three layered media are studied by forward simulation, and the dispersion curves of some assumed typical model parameters are carefully analyzed. Through the analysis, we can see that the dispersion curves are not intersected with each other, so we have a clearer understanding of this problem. It is pointed out that the characteristic of time dispersion curve exists in low-speed weak interlayer, and according to the analysis results, the formation mechanism of zigzag dispersion curve is explained.)