轨道不平顺是车辆振动的主要激扰源，也是限制列车最高运行速度的主要因素之一，直接关系到列车运行的平稳性、安全性和舒适性。文章以秦沈客运专线轨检车实测轨道不平顺数据为统计样本，基于样本平稳性检验，采用FFT方法进行样本空间的谱估计，并由MATLAB编程得到轨道不平顺谱密度。基于轨道不平顺样本的总体平均，得出了谱密度频率平滑曲线和谱密度曲线拟合表达式，并与我国重载提速干线的谱密度曲线进行了对比分析。在此基础上，对秦沈客运专线的轨道状态进行了评估。

The track irregularity which is the main vibrating resource of the vehicles and one of the main factors to limit the train highest speed, plays a very important part in the safety, stabilization and comfort of the trains. The statistic samples used by this paper are collected by track geometry inspection car from Qin-shen special line for passenger transport. Based on the stationary character test of the samples, FFT method was used to evaluate the spectrum of the statistical sample space, and MATLAB soft was used to get the PSD(power spectral sensity) of track irregularities. Based on statistical average of the samples of the track irregularities, frequency smoothing of the PSD and coupare with PSD of the main-line of Chinese railway were made. The curve to the PSD was fit. Then the track state of Qin+shen special line for passenger transport was evaluated.