The working performance of an optical communication system is not only related to the light source, but als-o to its transmission medium. With the development of fiber optic technology and the pursuit of longdistance trans- mission in the field of optical communication, optical amplifiers have emerged. Optical amplifiers can directly amplify optical signals and have great application value in the field of communication. Summarized the basic p-rinciples and development of optical amplifiers. Firstly, the concept, classificaee types of optical amplifiers were introduced, inclu- ding their working princ-iples and performance. Then, the current situation of various types of optical amplifiers at home and abroad was analyzed. Finally, the future development of optiction, and principle of optical amplifiers are in- troduced. Then, the key technologies of the thral amplifiers is prospected.