Abstract: The invention discloses a design method of a wavenumber linearity dispersion optical system and an imaging spectrometer, including: building an optical system including a grating, a prism and an objective lens that are sequentially arranged, the grating adjoins the prism; defining a linearity evaluation coefficient RMS; assigning a minimum value to the linearity evaluation coefficient RMS through adjustment to the vertex angle of the prism, when the linearity evaluation coefficient RMS is at minimum, the vertex angle of the prism being ?1; acquiring compensations for distortion and longitudinal chromatic aberration of the objective lens based on the interval between equal-difference wavenumbers on the image plane when the vertex angle of the prism is ?1; and optimizing the objective lens based on the compensations for distortion and longitudinal chromatic aberration of the objective lens to obtain an optimized optical system.