FM信号受单音干扰时，有时无法获取干扰信号信息，但易获取输入信号和输出信号信息。提出将均方误差公式进行改进，并与干信比这一指标相关联，间接对FM信号进行单音干扰效果评估的方法。首先，建立了FM信号仿真模型，分析了不同信噪比下FM解调信号的波形失真情况；其次，分析了FM调制信号受到单音干扰时，在不同干信比下FM解调信号的波形失真情况；然后，用均方误差公式来表示模拟信号失真度，分析其与干信比的变化曲线，并对均方误差公式进行改进，仿真研究后得到新的评估指标；最后，分析了新评估指标与干信比和占空比的关系。

Sometimes we can not obtain the interference signal information, but can easily obtain the input signal and output signal information when FM signal has got single-tone interference. So we propose to modify the mean square error and make it be associated with jamming to signal ratio(JSR), then we evaluate indirectly the FM signal single-tone interference. First, we establish the simulation model of FM signal and analyze distortion of FM demodulated signal under different SNR and different JSR. And we analyze the relation between JSR and mean square error which is used to express analog signal distortion. Then we modify the formula of the mean square error and obtain the new evaluation index after the simulation. Finally, we analyze the relation among the new evaluation index, the JSR and the duty cycle and get the conclusion.