The development of high power fiber lasers is faced with many technical bottlene cks,such as various nonlinear effects and unstable output modes and power etc.,b ut fortunately,large mode area and single-mode fibers are considered to be the main method to solve such problems.This paper summarizes the various typical lar ge mode area and single-mode fiber,expounds the structure characteristics and the realization principle of various fiber,focuses on t he key index such as the mode field area,output power,bending resistance characteristics,laser beam quality and fabrication difficulty,etc.The practical application value and the various deficiencies of various large mode area and single-mode fiber are obtained,which will provide an important reference for the related research and design of the large mode area and single mode fiber.Finally,a new type of large mode area and single mode gain fiber with helical hetero-cladding designed by the author thermselves is introduced in detail.The fiber core diameter can be adjusted flexibly in the range of 50－200μm.and compared with many other fibers,this kind of fiber is also rel atively easy to fabrication,thus,it is expected to be a new research direction in large mode area fiber field.