Abstract: At present, electromagnetic ultrasound has been widely studied in the fields of thickness measurement and nondestructive testing, but there is little research on bolt axial force measurement. In order to promote the application of electromagnetic ultrasound in bolt axial force measurement, in this paper, the process of electromagnetic ultrasonic excitation and propagation is simulated by establishing multi-physical field finite element method. Create a two dimensional bolt model, the signal of longitudinal wave propagation inside the bolt is obtained by electromagnetic ultrasound, and the stress distribution inside the bolt under axial load is obtained by finite element simulation. The finite element calculation shows that there is a certain linear relationship between axial load and acoustic time difference, and the linear relationship is affected by axial load. Different clamping length will affect the stress coefficient of the material, and the product of the tightening length and the stress coefficient is a fixed value.The test results show that both the finite element simulation results and the real test conditions show that under the action of axial stress, the ultrasonic propagation time increases, and a good linear relationship is presented with the axial stress.