Comparing with steel structure,aluminum and its alloys have the advantages of light material,no low temperature brittleness,corrosion resistance and easy pressure processing. Although the principles of the structure design and welding for aluminum alloy do not change comparing with steel structure,but the strength,elastic modulus,density,thermal conductivity and thermal expansion coefficient of aluminum alloy are significantly different from steel,so the strength design and joint details of welded joint are quite different from the steel joints. The main point of this paper is the weakening of the strength of welding heat affected zone, the details of welded joints including groove type and back protection and so on. The former is analyzed by EN1999-1-1 and the latter is analyzed by ISO9692-3 and EN1011-4.