In order to investigate the effect of cyclic loading waveforms on stiffness softening of structural soft soil,marine soft soil samples taken from Tianjin Harbor Bonded Area in Tianjin Binhai New Area will subject to cyclic loadings with varying waveforms and amplitudes.It is observed that the effects of varying loading waveforms like square wave,sinusoidal wave,and triangular wave do not have an apparent influence on the rate of stiffness softening when the loading amplitude is below the threshold stress.On the contrary,when the amplitude is much higher than the threshold,the rate of stiffness degradation for square wave is the fastest,and sinusoidal wave comes the second,while triangular wave is the last.Analyses are conducted on softening indices degradation curves under cyclic loadings with varying waveforms and amplitudes.Finally,the expression of softening index degradation considering both loading waveforms and stress amplitude is obtained.