Through coupling the light fields of multiple imaging with a microlens array and phase modulation with multiple micro-mirrors, the snapshot interference imaging spectrometer achieves the simultaneous detection of the image and spectrum of a dynamic scene. The substrate processing accuracy and film surface stress cause the bending deformation of the step surfaces in the multiple micro-mirrors and further affect the quality of the spectrum and imaging. In this paper, the surface shape error characteristics of bending deformation of the step surfaces in the multiple micro-mirrors were analyzed to build a light field transmission model of the step surface shape error. The calculation results show that different distributions of the step surface shape error produce different intensity changes in the interference image point array in each field of view and different noise distribution characteristics in the recovered spectrum. The step surface shape error introduces a phase error into the recovered spectrum in different imaging fields and modulates the intensity distribution of coherent image points. The reconstructed spectrum error increases monotonically with the absolute value of the step sagittal height of the two multiple micro-mirrors. This relationship can be leveraged to evaluate system performance with the measured value of the step sagittal height and provide theoretical guidance for device fabrication.