Abstract: In order to study the mechanism and propagation of the shear wave generated by EMAT (electromagnetic acoustic transducer) in continuous casting shell, the Q235 billet with shell thickness of 10~50 mm is taken as the re-search object. The electromagnetic ultrasonic model of pulsed electromagnet and spiral coil is established by using the finite element software COMSOL. The distributions of electromagnetic field, force field and sound field in continuous casting slab under different EMAT parameters are analyzed. The results show that the EMAT made by the combination of the pulse electromagnet and the spiral coil can excite the ultrasonic shear wave in continuous casting shell. The effects of the coil winding number, inner radius, and radius of coils on the transfer efficiency decrease in turn. When the radius of the pulse electromagnet is larger than the size of the spiral coil, the efficiency of generating transverse wave is the highest. The smaller the thickness of the shell causes the higher the optimal excitation frequency, the higher the precision and the faster the attenuation. The frequency of 1.1 MHz is chosen as the optimum excitation frequency for the Q235 billet with the shell thickness of 10~50 mm.