Aiming at the problem that the calibration results of the transmissometers cannot be traced to the meteorological optical range (MOR) defined by the World Meteorological Organization (WMO). We designed an indoor calibration light source of the transmissometers based on spatial light modulation, focusing on the design of a non-intersecting Czerny-Turner spectroscopic system which achieved a spectral resolution of less than 1 nm in the range from 380 nm to 780 nm. Then, the calibration light source’s spectrum matching model is established and the digital micromirror device (DMD)’s surface illuminance distribution law is simulated and analyzed. Finally, the MOR error of the calibrated light source is inverted. The results show that the simulation spectrum error of the 2 700 K absolute color temperature is below ±7.4% in the wavelength range from 380 nm to 780 nm, and the MOR error meets the requirements of the International Civil Aviation Organization in 40—2 000 m of MOR.