Due to the restriction of manufacture precision to beam splitter in spatial modulated Fourier transform infrared spectrometer, the wedge error will be existed on the substrate of beam splitter. Through the analysis of the propagation characteristics of the beam in beam splitter, the deviation of optical path difference caused by the wedge angle is gained, and then the functional relations between interference irradiance and wedge angle error, recovered spectrum and wedge angle error are obtained. The result shows that the wedge error can induce the spectral line shift to lower frequency and reduce the spectral resolution by means of simulation. After the theoretical analysis, the error tolerance of wedge angle under the wavenumber precision and spectral resolution is gained. Aiming at the interferogram intensity distribution influenced by wedge angle, a method of spectrum correction resolving the linear equation by discrete spectrum sequence is put forward, and the correction effect is proved well.