Abstract: Electromagnetic ultrasonic testing technology is widely used in equipment detection under extreme high and low temperature conditions, or without grinding because of its advantages of no coupling and non-contact detection. The sensitivity of electromagnetic ultrasonic flaw detection is an important representation of the ability of electromagnetic ultrasonic testing. However, the normal incidence electromagnetic ultrasonic flaw detection sensitivity is affected by equipment, probe, materials tested and other factors, and the actual performance is uneven. In this paper, the influence of different coil diameter and excitation frequency on the sensitivity of electromagnetic ultrasonic detection was studied, and a new electromagnetic acoustic transducer was designed based on the simulation results. The experimental results show that the sensitivity of the optimized electromagnetic acoustic transducer has been improved to some extent, and it can detect the φ2mm flat bottom hole in carbon steel. The comprehensive simulation and experiment showed that the sensitivity of electromagnetic ultrasonic flaw detection can be improved by reducing the outer diameter of the coil and increasing the excitation frequency.