Abstract: The 304 stainless steel elbow of a methanol scrubber pipeline cracked during use. The causes of elbow cracking were analyzed by means of macroscopic observation, chemical composition analysis, mechanical property test, fracture analysis and metallographic examination. The results show that stress corrosion cracking occurred on the elbow, which was caused by poor welding quality, high residual stress and service in corrosive environment containing sulfur elements and other factors.