Abstract: The tailings strength parameters is the key factor that affects the analysis of tailings dam stability． Based on triaxial tests under high stresses，the nonlinear strength property of tailings was validated． The results showed that the triaxial consolidation undrained shear curves had obviously softening characteristics，and the degree of strain softening increased as the stresses increased． According to triaxial stress-strain curves，an improved hyperbola model was set up for describing the phenomenon of tailings sand strain softening． The quadratic parabolic and power exponent function of envelope lines were adopted to describe the nonlinearity of strength characteristics，and the comparison results showed that the power exponent function of Mohr envelope had high precision as the criterion of breaking strength of tailings sand under high stresses． The function of equivalent normal stress and tangent value of internal friction angle indicated that the internal friction angle of tailings sand under high stresses was not a fixed value，but had nonlinearity characteristics of power exponent function．