Abstract: In this paper,the two-dimensional finite element model of surface-breaking tilted cracks is built,and the Sarmar Absorbing boundary condition is applied in this model.The ultrasonic wave exciting and propagating on the model and scattering on the tilted cracks is investigated,using ultrasonic spectral method to size different types of surface-breaking tilted cracks by numerical simulation.In order to show the scattering and complex mode-conversion clearly,the results are presented in the form of snapshots.And then,on the basis of spectral analysis to the transmission single,the relationship of Absorbing frequency and the slot parameters of angle and depth is obtained.