The Offner imaging spectrometer was built on the basis of the double mirror system, and its initial structure was obtained through solving optical path function. Through simulating and optimizing the initial structure using professional optical design software (Code V), the high image quality of spectrometer was obtained. Its root mean square spot diameter decreased obviously, and modulation transfer function curves in meridianal and sagittial had good imaging results. The study can eliminate overly complex aberration derivation process, and obtain high image quality Offner spectrometer structure in a wide spectrum (400~1 300 nm). It can provide a theoretical basis for the construction of the spectrometer.