Abstract: Friction stir welding (FSW) is used to solve the problem of the poor solderability of 7075 aluminum alloy. However， the complex changes of temperature and flow field are prone to cause defects. In this work， FLUENT software was used to study the changes of temperature and flow field of 7075 aluminum alloy during welding and the simulated results were verified. It is found that the temperature on the advancing side is higher， the flow rate is lower， and the maximum temperature appears inside the shoulder edge. When the rotation speed of the stirring head is higher， the welding speed becomes smaller， associated with a higher welding temperature. Meanwhile， the flow rate is faster and less affected by the welding speed. Under the conditions of the rotation speed-welding speed parameters of 800r/min-100mm/min，the defect-free weld can be achieved.

Key words: friction stir welding (FSW); 7075 aluminum alloy; FLUENT; temperature field; flow field