Abstract: The artificial freezing method and the soil in seasonally frozen soil areas usually undergo freeze-thaw cycles under a certain confining pressure. Affected by the freeze-thaw confining pressure and undrained conditions, the residual excess pore pressure of the melted soil results in that the soil is not in a fully consolidated state. Therefore, conducting researches on the undrained mechanical properties of soil under this condition is of great engineering and scientific significance. In this study, the undrained triaxial shear tests and microscopic scanning tests on the remolded muddy clay after freeze-thaw cycles using the self-developed temperature controlled triaxial apparatus are conducted. The effects of freeze-thaw confine pressure, the freeze-thaw cycles and freezing temperature on the mechanical properties of post-freezing and thawing silty clay are analyzed. Compared with that without no confining pressure, the number of flocculation structures and pores in the soil increases after freeze-thaw under confining pressure, thus the weaking effects of freeze-thaw cycles on the strength and modulus of soil are accelerated. As the freezing temperature decreases and the number of freeze-thaw cycles increases, the weakening effects of muddy clay become more obvious.