Abstract: After many experiments,structure and properties of FSW and the relationship between properties and welding parameters were analyzed on the base of optimized welding parameters.It shows that industrial pure Cu has good weld ability,optimized welding parameters can make a joint more strength than the base-material.Metal in the nugget zone undergoes coupled thermomechanical process and plastically deformed.As a result,a lot of grain cracked and recrystallized.The thermomechenicallly affected zone can be divided into recrystallisation zone,incomplete recrystallisation zone and dynamic recovery zone.