Deformation of crack-tip crazes was measured on poly(vinyl chloride) by the optical interference method when the fatigue crack grew discontinuously. The changes in the craze displacements and stresses during a crack growth retarded period were then analysed. With load repetition, crazes increase their size and deform rubber-elastically. Employing the inverse Langevin approximation, a model was proposed that attributes the increase of rubber-elastic extension to the increase of random links between tangled junctions of molecular chains in craze fibrils through disentanglement. The number of links was found to increase almost linearly with repetition. The model explains the change of craze stress-extension relation and also the difference of fracture-surface roughness.