对淬火材料表面淬硬层深度进行无损检测是当前的研究热点之一。但目前在利用脉冲涡流检测技术定量检测淬硬层深度的研究中，主要关注的是时域，这种方法容易受到干扰，为此提出基于频谱特征的淬硬层深度脉冲涡流检测方法。该方法首先在脉冲涡流检测淬硬层深度原理的基础上，建立了两层仿真模型；分别在时域和频域分析了不同深度下的检测信号，提出在频域下对淬硬层深度定量检测的频谱新特征量——频率；使用频率特征量计算了淬硬层深度，结果显示频率特征量与淬硬层深度具有良好的线性关系；最后，采用试验的方法对仿真结果进行验证，试验结果证明了所提出的频率特征量的正确性。

Nondestructive testing of the depth of hardened layer for the hardened material is one of the research hotpots. And nowadays, the pulsed eddy current (PEC) testing method has been used in this field for its quantitative measurement of case hardened depth. However, more attentions in the studies were paid to the time domain and its limitations were easily found. Accordingly, a new method is proposed based on the spectrum characteristic. In this method, a two-layer simulation model is established based on the principle of the testing of case depth with PEC. Next, the detection signals at different case depths are analyzed in time domain and frequency domain, respectively, and frequency is used as a new frequency spectrum characteristic value to quantitatively determine the depth of hardening zone in frequency domain. Then, the frequency is applied to calculate the case depth. The results show a good linear relationship between the frequency and case hardened depth. Finally, the simulation results are validated by the experimental method. The experiment proves the correctness of the proposed characteristic parameters.