Abstract: The semi-analytical model used for the calculation of ultrasonic field was proposed based on Rayleigh Integration and Pencil method, and the semi-analytical model used for the calculation of crack face, crack edge and inclusion echo was proposed based on Kirchhoff approximation, GTD and Born approximation. An ultrasonic testing calculation and anlysis system(UT-CAS) was deveopled based on these models. UT-CAS could give a fast calculation of the radiated acoustic field and defect echo, and was helpful for data analysis, performance demonstration and NDT training.