With the great improvement of microscope property, the eyepiece of microscope is required to have a larger field of view, high magnification, and better imaging quality. Because of the external aperture stop and short focal length, the design difficulty of microscope eyepiece lies in how to correct the distortion and other off-axis aberrations caused by the large field of view, and how to obtain an eye relief that meets the requirements for human observation is also important. The main aberrations of the eyepiece optical system, especially the effect of the optical system with distortion on imaging is analyzed in this paper. The freeform surface is applied to the distortion correction of the optical system of the microscope eyepiece. A wide-angle microscope eyepiece with field of vision of 60° and a magnification of 25× is described in this paper. The full-field distortion is less than 5%. The microscope eyepiece adopts a five-piece three-element structure, in which the freeform surface lens is made of plastic material and is symmetrical about the XOZ plane and YOZ plane. A high-performance microscope eyepiece design with simple structure, easy processing, and low cost is realized.