Based on the concepts of elastic wave velocity of skeleton and reinforced cohesion, the change of velocity resulting from the variation of soil density with the different saturation is distinguished from that caused weakened reinforced cohesion. In the condition of the same confined press and saturation, the elastic wave velocities are measured before and after soil samples are dynamically loaded, so that the elastic wave velocity changed by dynamic load is distinguished from that by soil nature characteristics. Some regular patterns of reinforced cohesion and velocity in loess under different saturation and dynamic load are discussed in a preliminary way.