Ultrasonic wave velocities in a plastically deformed medium are known to depend upon its microstructural material properties. Therefore, one of the authors proposed the theoretical modeling of an ultrasonic nondestructive method to evaluate plastically deformed states. In the previous papar, it was reported that the good agreement of the experimental results with the simulated subsequent yield surfaces and the longitudinal wave velocities under combined stress states of an aluminum alloy using internal state variables of an anisotropic distortional yield model, which were determined to achieve a good fit for the experimental reults of the longitudinal and transverse wave velocity changes under uniaxial tension test, was obtained. In the present paper, the transverse wave velocities propagating an aluminum alloy in combinations of tension and torsion are numerically simulated and then compared with the experimental results to examine the accuracy of the proposed theoretical modeling of an ultrasonic nondestructive method. Moreover, the plastic anisotropy growth under combined stress states is also evaluated via the proposed ultrasonic method and results suggest that velocity changes of the longitudinal and transverse waves under plastic deformations depend on plastic stress and strain states, respectively.