Aiming at different types of CCDs with a finite number of pixels, a spectrometer with low wavenumber, high resolution, and wide-spectrum is designed, which is of great significance to improve the optical performance of Raman spectrometer and meet the needs of integration. A low wavenumber high-resolution Raman spectrometer with an excitation wavelength of 532nm, spectral range of 10~2500cm-1, and resolution of 3cm-1 is successfully designed for 2048 pixels CCD based on Czerny Turner M-type optical structure and cylindrical lens to improve the sagittal aberration. The point diagram, RMS (root mean square) radius and modulation transfer function (MTF) curve of the imaging system effectively prove that its optical performance fully meets the design requirements.Then,based on this optical structure,the CCD is replaced by another type of 1024 pixels CCD. By selecting the grating with a stronger splitting power, optimizing the grating angle, and fine-tuning the position parameters of the focusing lens and image plane, the spectral range of the Raman spectrometer is 10~1800cm-1, and the resolution is improved to 1.8cm-1. These two sets of optical paths make full use of the number of the limited pixels of CCD and effectively achieve high resolution and wide spectrum. At the same time, the position of the optical elements of the two sets of optical paths changes little, which effectively ensures the optical-mechanical integration design requirements of a multi-model CCD spectrometer. The work of this article not only ensures the integration requirements of an optical-mechanical system of a spectrometer, but also meets the design requirements of low wavenumber, high resolution, and wide spectrum.