Abstract: With the rapid development of infrared technologies, optical systems with dual FOVs have been applied in all kinds of fields. The system with dual FOVs belongs to the simple zoom optical systems. The realization modes of zooming comprise of the independent zooming, rotary zooming, insert zooming, axial zooming and so on. Based on the analysis of zoom modes, a new mode of zoom optical system has been developed, which realizes the dual FOV optical system by sharing secondary imaging lenses. By the mode, the FTM value of the dual FOVs can be made to approach to the diffraction limit, and the accuracy of the optical axis can be improved. It decreased the moving mechanisms and reduced the difficulty of the system assembly.