Abstract: In order to study the fracture performance of cement soil, the notched semi-circular bending (NSCB) specimens were used, and the mode I fracture test was carried out. The effects of crack length, cement content and curing age on the fracture toughness and fracture energy of cement-soil were studied. The results show that: (1) When the diameter of the cement-soil NSCB specimen is D=150 mm, the crack length-diameter ratio a/R=0.4 and 0.5 are reasonable; with the increase of a/R, the peak displacement and peak load will gradually decrease, and the fracture toughness shows a trend of decrease. The fracture energy has a quadratic function relationship with a/R; (2) With the increase of cement content, the peak displacement gradually decreases, and finally tends to be horizontal, while the peak load will gradually increase, and at the same time, the sample shows typical brittle failure when it fails; fracture energy and content increase as a quadratic function. Fracture toughness and dosage increase linearly; (3) With the increase of curing age, the peak load and peak displacement gradually increase; fracture energy and fracture toughness increase with curing time as quadratic function. Compared with pure clay, the fracture performance of cement-soil is significantly enhanced.