This work uses different size of strain gages (Gage Grid Length: 10mm, 1mm, 0.2mm) to measure the stress distributions of metal (Al 6061-T6) and composite (laminates of [0/+45/90/-45]2S and [0/90]4S layers ) with a central circular hole and a crack. Both the SCF (Stress Concentration Factor) and SIF (Stress Intensity Factor) are found to consider the stress scatteredness of experimental data in contrast to micro- mechanics. To understand the strain gage size effect is our main purpose in measuring both types of materials. The size effect of strain gage we find appears obviously in the measuring position with stress changing significantly. We find that the size of strain gage is bigger; the error of stress is higher. Analyzing the stress scattering around a central circular hole, we obtain the experimental result that the stress will first reduce drastically from central circular hole edge and then keep uniform. In analysis of the stress scattering around the crack tip, we observe that first stress rises quickly from the specimen¡¦s free edge to the top of crack tip with a maximum value, and the stress keeps a nominal value in the specimen central part. Comparing the empirical result of SCF and SIF, we find that the data of 0.2mm of strain gage close to the theoretical solution, while those of 1mm and 10mm strain gages appear inexact in measuring and calculating SCF and SIF.