The effects of FSP (friction stirring processing) on microstructure and properties of the Al3Zr/6063Al composite were investigated, which was obtained in 6063-5wt%(K2ZrF6) system. OM, XRD and SEM were used to observe the morphology, distribution and dimensions of in-situ Al3Zr particles, and then the properties were analyzed. It is found that reinforcement particles of the composite are finer and more uniform after FSP; matrix grains crush and grain shape changes; tensile strength and elongation become larger; the composite shows superplastic deformation, especially when the deformation temperature is 500 oC and strain rate 1.67×10-2 s-1, it achieves 348.16% elongation rate.