Abstract: Ultra high toughness cementitious composites (UHTCC) is a new material with ultra-high toughness and good durability. Its compressive toughness index is an important index to evaluate the toughness of UHTCC. 5 groups of UHTCC with different fiber contents were tested under uniaxial compression after ultra-low temperature, and the evaluation index of compressive toughness of UHTCC under ultra-low temperature was studied, and its deformation capacity was equivalent analyzed. The experimental results show that within a certain range, with the increase of fiber content, the compressive strength and toughness of UHTCC are significantly improved, but beyond the optimal content range, the performances are not improved, but are slightly decreased; ultra-low temperature has a certain improvement on the compressive strength of UHTCC, when the temperature is reduced to −196℃, the axial compressive strength can be increased by 74.42%, but it shows obvious fragility.