In the visible and infrared regimes, optical nano-antennas are usually referred to metal nanoparticles and arrangement of the same, having distinct properties based on the localized surface plasmon resonance (LSPR). Optical antennas are generally characterized by their capabilities to strongly confine light, to enhance an optical response and even to modify emission directivity. On the basis of the principles of the surface plasmon, the charactistics of nano-antennas can be tuned by passive mode through changing design paramaters and active mode through an externally control. Optical nano-antennas have promising applications in the fields ranging from nano-optics, chemistry to biomedicine. This paper focuses on its most important functionalties and controlling modes, ended by a brief introduction in the applications in biomedicine.