Abstract: In order to conduct the research on deformation properties of unloading of pit excavation,a series of true triaxial tests were performed in tianjin soft dredger fills under the condition of unconsolidated-undrained with rigid-flexible composite true triaxial apparatus, it keeps that major principle stress fixed and intermediate principal strain ε₂≈0 and minor principle stress decreased. The results indicated that tangent compression modulus increases with increasing of compression stress, stress-strain relation ε₁ and ε₃ is linearity, poisson ratio is not match with classical soil mechanics theory,μ₃₁>0.5 and increases with increasing of compression stress, pore water pressure increases at first then decreases.