A method for detecting the content of β-polymorph in ε-HNIW by Fourier Transform Raman (FT-Raman) spectroscopy was developed. By analyzing the FT-Raman spectra of the four HNIW polymorphs (α-,β-,γ- and ε-),the peaks within 300~270 cm^-1 spectral region were used as the quantitative basis of purity detection for ε-HNIW. A series of different (β-,ε-)HNIW mixtures were prepared. The working curves were plotted by analyzing FT-Raman spectroscopy of the mixtures. There is linear relationship between the relative peak height of (β-,ε-)HNIW mixtures and the content of β-HNIW at 282.60 cm^-1. The correlation coefficient was 0.9995 and the standard deviation was 0.0158.