In this work, the Al-Si/Mg2Si in-situ composites were fabricated using casting technique, followedby repetitive equal-channel angular pressing(ECAP) to refine the microstructure.(ECAP) as sever deformation was carried out through a die made of high chromium carbon steel at250ºC for four passes of deformation.Microstructures investigation was conducted using an optical microscope, electron back scattering, EDS, elemental mapping and electron backscattered diffraction (EBSD). After sever deformation , the results showed fragmentation of eutectic Mg2Si and eutectic Si , reduction of the primary Mg2Si particle size , and fragmentation of the dendrite of Mg2Si particles to smaller ones. On other hand, the columnar α-Al phase changed to nearly equiaxed grains after severe deformation. The results of (EBSD)revealed that the grain size of the in site composite matrix showed decrease to less than5µm after four passes ,and the grains after deformation have more orientation of homogenization, and there are fine grains less than1µmin size surrounded by high angled boundaries