Effects of beam focus position was studied on the 2205 duplex stainless steel fiber laser welded joint shape and microstructure. By welding heat simulation and joint miscorstucture analysis. It was showed that the temperature field of the joint varied as the changes of laser beam foucs position changed. Besides, when laser beam focus position was moved downward, the width of weld and the number of pore in weld were decreased, but heat affect zone was the invariant. In addition, the microstructure of 2205 duplex stainless steel was effected by laser beam foucs position. When laser beam focus position was positive, the Austenite content was the highest than other conditions. When laser beam was focused on surface, the Austenitic distribution in the weld became even.