Abstract: A new method of spectropolarimeter aimed at polychromatic light based on photoelastic-modulator (PEM) was proposed, which included a linear retardance oriented 0(-45) PEM and a polarization analyzer at 45(0). The light was first modulated by PEM, then pass through the analyzer and formed the modulated interference signal after detected by detector. Finally the incident light polarized spectra (S1、S2 and S3 of Stokes parameters) were obtained by Fourier transform of the modulated interference signal. The method reduces the complexity of polarized optical length measurement. The basic principle was introduced, the correctness and feasibility were verified through the corresponding numerical simulation.