The data obtained from a field test of irregularity of rail surface in Hu-Kun line, a CWR track, is processed by statistical analysis of maximum amplitude and one-third octave analysis. The result shows that the regularities of rail surface in joint areas of CWR track are worse in common. In general, the amplitudes of rail surface irregularities can get beyond 0.5mm/m, which exceed standard values in every wave length ranges, and the maximum of them can reach 15dB. The conditions of rail surface regularities in non-joint areas are better, and the rail surface irregularities from most of the test points are lower than 0.15mm/m, which do not exceed standard values.