This paper uses GCTS dynamic hollow cylindrical torsional shear apparatus and two cyclic loading waveform of sine wave and square wave. It considers the confining pressure, the influence of the vibration amplitude, frequency and the minor factors. It studies the dynamic characteristics of structural soft clay. The test results show the follows. When the dynamic stress is below the yield stress of soil structure, waveform's influence on the overall shape of the dynamic stress-strain relationship curve is very small. When dynamic stress exceeds the structure yield stress, stress-strain relationship is softening type. The softening degree of square wave is higher. Under the same conditions, square wave accumulated deformation is always greater than that of the sine wave. Waveform has an effect on pore pressure changes. The values of pore pressure under sinusoidal wave action is always greater than that of the square wave. Amplitude for the performance of pore pressure change is as follows:when the rising speed of stable amplitude is quick, the value is greater than the critical type amplitude under the action of pore pressure value. Namely the critical type amplitude under the action of pore pressure hysteresis phenomenon is serious. Yield strain and dynamic strength decrease with the increase of the vibration time trend, eventually tend to a certain value. Finally numerical size is related to the waveform. The sine wave is less than the square wave, which is contrary to the sine wave is greater than the square wave.