Abstract: There are two ways to improve the property of damaged steel structures: retrofitting and replacement． The cost of retrofitting is often far less than that of replacement of the whole structure． In addition，retrofitting takes less time，reducing service interruption． So retrofitting is always the first choice to repair steel structures． The traditional retrofit methods are based on the use of steel plates which are attached to the damaged area by adhesive bonding， welding，bolting，which have disadvantages，such as the increment of weight and production of stress concentration etc． Carbon fiber reinforced composite ( CFＲP) has excellent chemical properties and stability，when using it for strengthening damaged steel structures，it can improve their working behaviours，prolong fatigue life． It was summarized the research achievements both at home and abroad，such as: the increase of moment carrying capacity， the distribution of interfacial stress，the extending of the fatigue life of structural steel elements，which can be useful for the engineering application or further researches．