Abstract: In semi-infinite bars by viscoelastic model, the wavefront strength in wave propagation process will reduce, the intensity attenuation has the relationship with the properties of the viscoelastic material. In order to analyze the change situation of wave in the viscoelastic beam propagation, velocity and attenuation factor, based on fractional theory, the influence of related parameters is analyzed by the viscoelastic standard solid model on the wave velocity and attenuation factor. The given model can better describe the change of longitudinal wave in the propagation phase velocity and attenuation factor. On the basis of the complex compliance by the standard viscoelastic solid model, the influence about the order of the fractional derivative viscoelasticity differential operator, angular frequency and delay time on the wave phase velocity and attenuation factor are analyzed.The results show that, as the delay time value increases, the propagation phase velocity of the longitudinal wave in the viscoelastic linear standard solid semi-infinite bars is increasing and the attenuation factor is decreasing. With the increase of fractional derivative differential operators, the propagation velocity and attenuation factor has the trend of decreasing first and then decreasing.