The electromagnetic acoustic transducers (EMATs) possess the capability of generating Lamb waves. The waves manifest the characteristics of multi-mode, dispersion and weak singal, which limit the development and application of EMATs. To enhance the signal of Lamb wave EMATs, we proposed an optimal design method. By adding super-microcrystals between the permanent magnets and the coils, the eddy current in the surface of the permanent magnet was reduced and the eddy current in the specimen was increased. Meanwhile, the distribution of the static magnetic field was improved, and the signal intensity in the aluminum plate was enhanced. In this paper, the effect of ultra crystallite on electromagnetic ultrasonic signal was mainly studied. The finite element software was used to simulate and analyze the experiment. The experimental results show that the method can effectively enhance the intensity of Lamb wave signal.