Active infrared detection technology is widely used in fields such as aerospace, shipbuilding, bridges and chemical pipelines. In the defect detection of complex-shaped metals, pulsed eddy current thermography (PECT) has attracted much attention due to its non-contact, fast, safe and intuitive features. Current PECT applications are broad; however, research on PECT excitation device performance has been lacking. The electromagnetic induction coil is an important component of the electromagnetic excitation system. Its function is to generate a transient pulse current and induce a magnetic field in the member under inspection. While simple in form, its large power consumption and low efficiency do not permit great portability. The objective of this paper is to study steel crack detection. A coil with a U-shaped magnetic core was used for the PECT system. The magnetic force lines winding around the magnetic core produced excitations. Excitation performance was then analysed through a finite element simulation and verified in a comparison of experimental results. The excitation of the magnetism-gathering device has many advantages, such as higher energy transfer efficiency and better uniformity. Moreover, the heating power has a smaller effect on the lift-off distance, hence better detection of metal surface defects can be achieved. More importantly, PECT detection adds a greater degree of portability to in-service equipment. @en