Irregular geometry of rails results in difficult extraction of flaw signals during ultrasonic inspection. The multi-Gaussian beam model for transmission of ultrasonic waves in rail heads was built on the basis of the multi-Gaussian beam theory,the geometric parameters and acoustic performance of rail heads and the charac-teristic parameters of the probe and couplant.It was then used to study the distribution characteristics of the a-coustic field under different frequencies and wafer diameters.In the meanwhile,the influence of the incident angles and curvature radius on the sound field was observed.It also helped analyze the effective inspection area of the probe in various situations.The ultrasonic measurement model was built on the basis of the multi-Gauss-ian beam model and in combination with the Kirchhoff approximation scattering model,to predict flaw re-sponse signals in rail heads.The amplitude and phase of the main parts of both the predicted and the measured signals of a side-drilled hole in the rail head are in good agreement.This method is proved to be valid.The re-search results have great theoretical guiding significance for ultrasonic inspection of rails.%钢轨不规则的几何外形造成超声检测时缺陷信号难以准确提取。根据多元高斯声束理论，结合轨头的几何参数及声学性能、探头及耦合剂的特性参数，建立了超声波在轨头内传播的多元高斯声束模型，以此研究不同探头频率、晶片直径下轨头区的声场分布规律，探求入射角、踏面曲率对声场的影响，并分析各情况下探头的有效检测区域；基于建立的轨头内多元高斯声束模型，结合基尔霍夫近似获得的散射模型，建立超声测量模型，实现轨头内缺陷响应的回波预测。通过对轨头内的横通孔进行模型预测与实验检测，两信号主体部位的峰值峰位均良好吻合，验证了该方法的有效性，研究成果对钢轨超声检测工艺有积极的理论指导意义。
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