Abstract: The alkali embrittlement cracking is one of the most detrimental failures in welding. Several types of the constant rate technique were used to assess the susceptibility of low carbon steel and its welded joint to alkali embrittlement. They were the constant strain four-point bend stress corrosion test, the constant load tensile test,the disk specimen welded joint stress corrosion test and the constant load contilever beam test. Corresponding data were gathered by tests in 30 wt% NaOH solution at 117℃. Microscope, SEM and electrochemistry method were used to investigate the alkali embrittlement mechanisms. The test results in this paper have been utilized by certain aluminum factories and chemical engineering factories with desirable economical effect.