Imaging Interferometer (IIM) aboard on Chang'e-1 is a Fourier transform imaging spectroscopy. Spectrum reconstruction which converts raw interferometric data to spectral data is crucial to the signal-to-noise (SNR) property and spectral consistency, thus influences the usability of IIM data. Three modified periodogram method including periodogram with rectangular window (PRW), periodogram with triangular window (PTW) and Bartlett method are introduced for the spectrum reconstruction. We use the Spectral and Spatial Decorrelation method to calculate the SNRs, and use Apollo samples to calibrate the spectrum and validate the spectral consistency of the three methods. Experimental results showed that Bartlett method had better performance in both SNR and spectral consistency than other two methods.