Abstract: Metal magnetic memory(MMM)is one of the most potential non-destructive testing methods which can diagnose welding crack in early stage.The distribution regularities of metal magnetic memory two-dimension spectrum entropy were investigated in tension test condition with the X70 pipeline steel. Using the feature of amplitude spectrum entropy and braycentre frequency, the support vector machine method can distinguish the different state of stress concentration.With the detection instance, the diagnostic method of stress concentration state in weld was gained.Research shows that the stress concentration state within the ferromagnetic material can be identified by the two-dimension spectrum entropy distribution of MMM signal.It is a base for utilizing MMM to detect the micro-cracks.