Abstract: Fourier transforms spectrometer is based on Michelson＇ s interferometer,which can be used to obtain the spectrum of incident light. A homemade Fourier transforms spectrometer is established where a light dependent resistor（ LDR） is used as sensor. During the moving mirror moves through the normal direction of the mirror, the changes of interferometric pattern are recorded as intensity curve, and the intensity varies depend on the changes of optical path difference （OPD）. The coherence length of the incident white light is given based on this curve, and the spectrum of the incident white light is also obtained based on the Fourier transform of this curve.

Key words: Micbelson＇s interferometer, Fourier transforms spectrometer, coherence length, spectrum of white light