Abstract: Electromagnetic acoustic testing has been widely used in many industrial fields due to its non-contact characteristic, while it’s still restricted by the low efficiency and large signal noise. This paper studies a different ultrasonic method for steel plate surface inspection based on interference enhancement of Rayleigh waves. An electromagnetic acoustic transducer(EMAT) is used to generate the Rayleigh wave because of its advantage of no couplant interference with the acoustic wave propagation. With the self-developed EMAT that can be used for scanning inspection, a platform is set up to conduct the experiment of slots testing. Results show that the ultrasonic signal enhances 10%~20% when the transducer is placed in certain location from slots and this provides the possibility of using the enhancement to evaluate defects without analyzing the relatively weak defect reflections.