Abstract: Recently, the crack extension resistance curve for crack propagation was proposed based on the crack cohesive action, where energy dissipation due to aggregate cohesive action is the primary contribution. In addition, energy dissipation is closely related with the tension softening curve, i.e., cohesive stress-crack opening displacement curve. Recognizing this, the influences of softening curve on crack extension resistance GR are studied in this paper. Four different tension softening curves are examined firstly. The results show that crack extension resistance GR is sensitive to tension softening curve, and its feasibility depends on the accuracy of softening curve. Also, it is found that the characteristic points in crack extension resistance curve are corresponding to those on softening curve.