A direct method is proposed to study wave dispersion in stiff unidirectional fiber-reinforced elastic random composites. The present model is featured by a modified form of classical elastodynamic equations supplied with a simple differential relation between the displacement field of the composite and the displacement field of the mass center of representative cell. Explicit formulas are derived for the attenuation coefficient and effective phase velocity of in-plane P-waves, SV-waves, and anti-plane SH-waves, respectively. The efficiency and accuracy of the model are demonstrated by comparing predicted results (on the frequency for the maximum attenuation and effective phase velocity at frequencies below the bandgap) with a large group of known data reported in past decades. The proposed model offers a novel general method for dynamics of stiff unidirectional fiber-reinforced elastic random composites.