Abstract: According to the shear lag model and the actual distribution of whisker in composites, the bearing stress factors of matrix in composites was analyzed. By using the principle of X ray stress measurement, the bearing stress factors of matrix in composites was measured. The calculation result shows that the bearing stress factors of matrix in squeeze casting and extruded vol.20%SiC W/6061Al composites were 0.783 and 0.569, respectively. The experimental result confirmed that the bearing stress factors of matrix in two kinds of composites were 0.742 and 0.557, respectively. The bearing stress factor of matrix in composites from experiment was close to that from calculation.