In order to further study the fracture property of ultra-high toughness cementitious composite（UHTCC） under ultra-low temperature environment， five groups of UHTCC prefabricated crack notched beams with different fiber contents were designed. After ultra-low temperature and cryogenic treatment， three-point bending loading test was carried out. The fracture performance of UHTCC under ultra-low temperature environment was evaluated by analyzing and calculating the load-deflection curve of UHTCC. The results show that the performance improvement effect of UHTCC with the fiber content of 1.5% is the best. After the fiber content exceeding 1.5%， the performance of UHTCC is slightly reduced. The strength of UHTCC increases significantly after ultra-low temperature. When the temperature reaches -160 °C， the material shows obvious brittleness， and its ductility index， characteristic length and unstable fracture toughness are significantly reduced.