Explosion tests were conducted on pipe specimens to determine the effect of stress annealing. Pipe specimens, 400 mm diameter, 800 mm height and 20 mm thickness, were welded in four longitudinal and one circumferential joints. Specimen was filled of water to reduce the detonating effect of explosive shock wave, and then an explosive set in the center of pipe was detonated. Evaluation of the performance of specimen was provided by checking the circumferential strain on circumferential butt joint. Explosion test showed a remarkable difference which could not been examined by longitudinal bend test or V-notch Charpy impact test. Namely, the annealed specimen was fractured by explosion when the circumferential strain reached at 11%, while aswelded one at 6 %.