对结构进行动特性分析，为计算最低阶固有频率，常用等效质量法把多自由度系统简化为单自由度系统。本文研究在不同支承条件下变截面梁的等效质量计算法，推导了一系列计算公式。通过与有限元计算的结果进行对比，表明本文提供的算法具有较高的精度。 Dynamic characteristics of the structure of the analysis, in order to calculate the lowest order natural frequency, commonly used equivalent mass method to multi-degree of freedom system is simplified to a single degree of freedom system. In this paper, the equivalent mass calculation method of variable section beams under different support conditions is studied and a series of formulas are deduced. By comparing with the result of finite element calculation, it shows that the algorithm provided in this paper has higher accuracy.