Microsphere-assisted super-resolution microscopy is an emerging technique which can be used to overcome the diffraction limit of conventional optical microscopes and significantly enhance their resolution. This technique is very promising for various applications because of the simplicity of its operation, its label-free and real-time imaging nature and its ability to be performed under white-light illumination with commercially available optical microscopes. Although there are many impressive results coming out along with the development of this technique, most studies are about the imaging properties, imaging quality improvement and manipulation of microspheres. A comprehensive theory on the super-resolution mechanism is still missing. Within this context, the progress of the microsphere’s imaging theory and the numerical methods in simulating the near-field focusing and far-field imaging phenomenon of microspheres was reported in this paper. The challenges and the future of this technique were also discussed.