According to the demand of imaging spectrometers for mini satellite platforms, an imaging spectrometer based on a linear variable filter is designed. By using the linear variable filter as a light splitter, the miniaturization of system structure, the reduction of development period and cost and the improvement of spatial resolution, signal-to-noise ratio and reliability can be realized. Because the method is suitable for micro/nano satellite platforms, it has a good application prospect. According to the overall design, the related specifications are determined, analyzed and calculated. On this basis, the parameters of the optical system and the splitter system are designed. Finally, the overall signal-to-noise ratio of the system is analyzed. The results show that the system has good imaging performance and can meet the observation requirement. Thus, the expected design purpose is achieved. The theoretical basis is provided for the implementation of the system in next step.