The acoustic technologies of the mechanical properties assessment and diagnostics of steel rolled bars based on using contactless electromagnetic acoustic (EMA) transducers of longitudinal, shear and Rayleigh waves and a mirror-shadow technique on multiple reflections are presented. Dependencies of the structural sensitive acoustic factors (absolute values of longitudinal, shear and Rayleigh wave velocities, their changes during the mechanical loading, acoustoelastic coefficients, efficiency of EMA transformation) on elastic and mechanical properties, the quality of heat treatment, the structural and stress-strain state of steel bar samples from springing, low-alloyed perlite and chrome-nickel steels are investigated.