W-Mo composites with different mass fractions of W and Mo were prepared at 1473 K by Spark Plasma Sintering technique. The transverse and longitudinal wave velocities of the samples were accurately measured using the ultrasonic pulse echo overlap method, and the wave impedance values of the samples were then calculated. The results show that W-Mo system composites are of nearly full dense and can be regarded as a mechanical mixture system. The ideal mixture model was adopted to estimate the wave impedance of W-Mo composites. Comparisons with the experimental data demonstrate that the suggested model is sufficiently accurate to predict the wave impedance of W-Mo composites.