As a precision instrument, the microscope is typically used by researchers in criminal investigation, information forensics, biology, metallography, etc. However, the traditional microscope has a dilemma in that if it uses higher magnification, its field of view is smaller and its depth of field is more limited. Hence, it seriously challenges the endurance and brain of the observer to observe an object thoroughly. This paper proposes a wide-field and full-focus imaging method for solving the above problem. First, a high-precision multi-focus image acquisition platform is improved, and its motion displacement is used directly for image calculation, which greatly reduces the amount of calculation. Second, the focus area of each image is segmented by the mask generation algorithm based on a graph cut. Third, a fusion algorithm, whose contrast pyramid is based on the mask region, is proposed, which utilizes the position of the clear area on the mask pyramid to guide the fusion of the contrast pyramid. Finally, a fast and fault-tolerant stitching algorithm based on mechanical and optical parameters is proposed, which effectively eliminates the interference of the cumulative error and successfully completes hundreds of image-stitching tasks. The experimental results demonstrate that the proposed imaging system is obviously superior to the traditional image fusion algorithms and image-stitching approaches. Both the imaging effect and execution time are satisfactory.