Abstract: With the exploring of microscopic world, nano-technology and life science have been investigated under micron and nano scales. Compared with near-filed imaging methods, far-field microscopic technique has many advantages, such as long working distance and non-damage. However, the resolution of far-field imaging is restrained by the diffraction limit. How to overcome this limit has become the focus of many research areas. In this paper, the principle of breaking through the diffraction limit is introduced. The latest far-field methods based on the nonlinear effect, special light illumination, coupling elements and microsphere are briefly reviewed including their biomedical applications. Finally, the trend of the methods, which overcomes the diffraction limit in far field, is given.