A method of parameters design and optimization for single viewpoint infrared catadioptric omnidirectional imaging system to obtain sharp image for the whole field of view (FOV) by single shot is proposed. The initial system parameters are designed to meet single viewpoint constraint according to the application requirements. A concept of virtual depth of field in mirror is proposed to optimize refracted optical group parameters. The proposed method is verified by simulation results using the ideal system of software ZEMAX. Using the method can not only obtain sharp image for the whole FOV, but also meet the requirements like FOV and axial dimension. The simulation results also show that large diameter mirror helps to improve the quality of the image and large surface eccentricity helps to reduce the axial dimension.