Abstract: Heat exchangers in many large industrial boilers are made up of complex and dense boiler tubes. In the operation of the equipment, the damage of the tubes can be caused by corrosion, erosion, vibration and wear. In order to find out the wall defects of the dense boiler tubes, based on magnetostrictive guided wave technology, experimental research was carried out by using large CDQ boiler evaporator tube box. The research covered with MsS guided wave type and frequency selection, transducer arrangement and coupling mode, detection sensitivity and pulse echo signal analysis. Through field application and furnace tube dissection test, the characteristics, effectiveness and limitations of MsS guided wave technology in large boiler complex waste pipe inspection are presented.