A Schmidt corrector plate for cancelling the aberrations of spectrometers is designed based on the principle of a Schmidt system. A formula for the surface shape and a surface map of the Schmidt corrector plate are derived. Then, the imaging characteristics of the spectrometer systems with and without the Schmidt corrector plate installed are simulated and analyzed using the ZEMAX software. The results show that for the wavelengths of 350, 550, and 700 nm, the root-mean-square (RMS) radii of light spots on the image plane of the original spectrometer are 515.843, 563.074, and 885.820 μm, respectively. In contrast, with the Schmidt corrector plate installed, the RMS radii of light spots on the image plane are 287.441, 252.774, and 511.816 μm, respectively. For the wavelengths of 350, 550, and 700 nm, the spot sizes with the Schmidt corrector plate installed are reduced by 44.28%, 55.11%, and 42.23%, respectively. The proposed method for designing a Schmidt corrector plate provides a technical reference for improving the resolution of spectrometers.