A modified mixed-domain method is presented in this paper to model wave propagation in heterogeneous media. The previous mixed domain method is only accurate for weakly heterogeneous media. Both the phase and amplitude corrections are introduced to the mixed-domain method in order to model wave propagation in more strongly heterogeneous media. Two cases are studied to validate the modified method. A two-layered medium with density and speed of sound variation is first studied. A human skull with density and speed of sound variation is then used to further evaluate the accuracy of this method. Result from the angular spectrum approach is used as the benchmark for the layered medium and result from the MATLAB toolbox k-Wave is used as the benchmark for the case of skull. Simulation results show that the modified mixed-domain method is more accurate for strongly heterogeneous media.