Abstract: Due to the onconflict between the wide spectral range of measuring (276-700 nm) and the limited imaging area of CCD detector (14.3 mm10.5 mm), classical Czerny-Turner structure was not able to meet the requirements of design. Based on it, an innovative method applying two uniform plane diffraction gratings to separate the whole spectral range into two different sections was presented. The two separate spectral range, rotation and tilt angles of two gratings were obtained through theoretical computation. The optical software ZEMAX was used to simulate and optimize the optical system by multiple configuring parameters. The simulation results show that two spectral bands are detected on the imaging plane. Their spectrum width is 14mm respectively, and the center distance between them is 8 mm. The spectral resolution is less than 1 nm and the aberration is substantially corrected. It indicates that the method is a good solution for the situation of wide spectral measurement range and limited imaging dimension of CCD detector in the meanwhile.