Abstract: Cracks were found at weld seam and base metal near the cylinder of dyeing cylinder heat exchanger of a textile company during maintenance process. Cracking causes of the heat exchanger weld seam were analyzed by means of macroscopic analysis, chemical composition analysis, hardness test, metallographic examination and chloride test. The results show that cracking mode of the weld seam and base metal near the cylinder of the heat exchanger was stress corrosion cracking. Due to the high mass concentration of chloride ion in the steam condensate, stress corrosion cracking occurred in the weld seam under the joint action of welding residual stress and working stress.