Abstract: In order to get metal magnetic memory(MMM) signal characteristics under single cycle tension loading and multi-cyclic fatigue loading, 20 steel welded plate specimens were tested by experiments. In single cycle tension experiments, the loading is increased from 20 kN to 60kN at 10kN interval space. In multi-cyclic tension fatigue experiments，the static loading is 35kN and the stress ratio is 1/6. The results showed that MMM signals had fluctuations throughout the specimens under the initial state because of the residual stress distributed uniformly on welded joints. With the increment of tension loading, internal stress was redistributed again and MMM signal tended to be stable. In the cycle cumulative experiments, MMM signals show a loop-arising trend along with the increase of cycle numbers, reflecting the magnetic elastic variation effect. By establishing the relational model between the damage degree and the magnetic memory signal, the fatigue residual life of welded joints can be forecasted.