Abstract: A finite element analysis of three dimensional elastic problem on the stress distribution round a small blind hole with a flat bottom of which both the depth and the diameter were 2mm was carried out in order to analyse closelv the effect of a small blind hole on the strength of the welded structure measured. The calculated results indicated that the stress concentration produced by a small blind hole is not more serious than that by a hole through a plate under a uniaxial stress. The position of the maximum stress concentration is on the wall of hole, near the surface of the specimen and perpendicular to the tensile stress, rather than on the corner of the hole bottom. In addition, a three dimensional analysis of a photoelastic mechanical experiment was carried out. The test results of stress distribution is basically identical with those calculated.