为掌握电力系统中机电扰动传播的本质，基于有限长均匀链式离散电力系统，在不考虑发电机的内阻抗时，研究机电扰动在系统中传播的反射特性。通过拉普拉斯（Laplace）变换，推导出冲激函数和阶跃函数形式的扰动作用下发电机的转子角和功率增量随时间变化的解析表达式，给出离散模型中扰动传播的反射公式，与连续体模型中机电波的反射公式相同，说明了电力系统的机电动态可表达为机电扰动传播过程中多次反射的叠加。最后通过一个实例验证了所得结论的正确性。该结论对于认识大规模电力系统的频率在时间和空间上的分布特性、揭示机电动态现象的内在机制具有一定的理论意义。“,”In order to grasp the essence of electromechaincal disturbance propagation in a power network, based on a finite length uniform chain discrete power system, the reflection characteristics of electromechanical disturbance propagation were studied after the machine internal impedance was neglected. Utilizing the Laplace transformations, the analytical expressions of the machine rotor＇s angle increments and power increments at all buses were derived under the impacts of disturbance with the form of the unit-impulse function and the unit-step one. At the same time, the reflection formula of electromechanical disturbance propagation in the discrete model was also presented, as the same as that of electromechanical wave propagation in the continuum model. All of these above show that the electromechanical dynamics of power system can be represented by the multiple superpositions of the reflections process of electromechanical disturbance propagation. Finally, the conclusions presented in this paper are validated through a simulation case, as have some theoretical meanings for understanding the time-space distribution characteristics of large-scale power systems＇ frequency and revealing the internal mechanisms of electromechanical dynamic phenomena.