Abstract: To compare the characteristics of Metal Magnetic Memory Technique(MMMT),a nondestructive testing method applied to two different materials(ferromagnetic and paramagnetic materials),AISI304 and Q235B vessels has been developed by MMMT respectively.The results show that the weak-magnetic AISI304 material becomes magnetic obviously after welding,indicating that the new MMMT method is feasible in testing weak-magnetic materials.It is also demonstrated that the disorderly magnetic signals of pre-heat treatment welds of Q235B become uniform after heat treatment.At the same time,heat treatment does not alter the basic characteristic of abrupt change and overturn of magnetic signals at the welds of Q235B vessel.