By means of adding micron Ni powder in the Friction Stir Processing (FSP) period and the resultant rapid in-situ reaction between Al and Ni under FSP condition, Al3Ni-Al composites were obtained on Al alloy 1100-H14 surface layer. The microstructures of the surface composites were analyzed by SEM and EDS, the phase composition was examined by XRD, and the microhardness was also measured. Results show that Ni powder was broken sufficiently under the severe thermal-mechanical coupling of FSP, and the broken Ni in-situ reacted with Al matrix rapidly to produce sub-micron or even nano particles of Al3Ni; while a few micron particles of residual Ni were covered by Al3Ni layer and homogeneously distributed in Al matrix with fine Al3Ni particles. Therefore, the microhardness of the composites increased greatly and reached to 818.3 MPa, 2.4 times of that of Al alloy 1100-H14.