Abstract: Magneto acoustic emission (MAE) is a new nondestructive testing technology. Magnetization is one of the main factors affecting the intensity of MAE signal. Therefore, the magnetization effect of different size U-yoke on Q235 sample is different when the amplification factor of power amplifier of magneto acoustic emission magnetization device and the ampere turn number and magnetic circuit of coil are fixed. Using ANSYS Maxwell electromagnetic field simulation software, the finite element simulation of U-yoke with different sizes is carried out, and the influence of different winding modes of coils on the magnetization effect of the sample is analyzed, in order to find out the optimal size of the yoke. According to the simulation results, the smaller the distance between magnetic poles, the stronger the magnetic field produced, and the better the magnetization effect of Q235 sample. The magnetization effect of Q235 sample increases first and then decreases with the increase of the thickness of magnetic poles, and hence conclusion is drawn that winding mode has no effect on the magnetization effect of Q235 sample is drawn.