The refill friction stir spot welding (RFSSW) process of aviation-grade high-strength aluminium alloys 2B06(1 mm) and 7B04 (1.5 mm) was investigated using the ABAQUS finite element method to analyse the temperature fieldand Eulerian volume fraction (EVF) field. The results indicate that the temperature distribution in the RFSSW isaxisymmetric and circular about the weld centerline. The stir zone (SZ) has the highest temperature, with the peak valueexceeding the solidus temperature of the material when the rotational speed surpasses 1 600 r/min. Moreover, the root voidfraction initially decreases but then increases with increasing rotational speed. This behavior is attributed to insufficientmaterial flow at low rotational speeds, which hinders complete root filling, and material adhesion to the tool at highrotational speeds, leading to volume loss and incomplete root consolidation.