Abstract: Constant strain bend and slow strain rate tests (SSRT) were used to investigate the resistance to sulfide stress corrosion cracking (SSCC) of 16Mn and 16Mn hydrogen-induced cracking (HIC) resistance steels and their welded seams in acid solutions with saturated hydrogen sulfide gas, The results show that all of sampies are sensitive to SSCC in the acidic solutions with H₂S. The mechanism of cracking is HIC and most cracks are transgranular type. The resistance to SSCC of 16Mn(HIC) steel with low content elements C, Mn, P and S is better than that of 16Mn steel. Otherwise, the welded seams have less resistance to SSCC than their matrix because of big crystals, inclusions, vacancies and defects produced in the process of welding, but the work of post welding heat treatment (PWHT) can increase the resistance of their welded seams.