In order to obtain the internal fine structure of biological tissues and living cells, the microscopic imaging technology is required to be capable of microscopy. In the wide-field fluorescence microscopy with dynamic speckle illumination, a series of dynamically changing speckle patterns are used to illuminate a biological sample in the whole field. The fluorescence sectioning images of sample’s three-dimensional structural are obtained by extracting intensely changing fluorescence signals in the focal plane. In this paper, the process of obtaining fluorescence sectioning images by the fluorescence microscopy is studied by theoretical analysis and simulation. Two main factors affecting the imaging quality of fluorescence sectioning image are analyzed, which are the number of original fluorescence images recorded by CCD and granularity of diffuser. The simulation results indicates that the imaging quality of fluorescence sectioning images first increases and then tends to saturation with the number of original fluorescence images increasing. It first increases and then decreases with the graininess of diffusers increasing. Considering the imaging quality and imaging time, when the number of original fluorescence images is 60 that is used to extract fluorescence sectioning images, and the granularity of diffuser is about 1000, the high spatial resolution fluorescence sectioning images with contrast higher than 85% can be obtained. Theoretical analysis and simulation research provide a theoretical basis and guidance for designing the system structure, implementing and optimizing the wide-field fluorescence microscopy with dynamic speckle illumination.