Slide-ring (SR) gel is a highly deformable polymer gel prepared by cross-linking rings on polyrotaxanes, in which ring molecules are threaded onto a linear polymer chain. The remarkable extensibility of SR gels is due to the stress equalization effect caused by the sliding of cross-links on polymer chains, which is called as ‘pully effect’. Photron high speed polarization camera system can observe the stress of deformation and fracture behavior at the crack tip of SR gel, due to the birefringence phase difference. The research discloses the difference blunting behavior of the crack tip with different concentration of SR gel. SR-02 gel (low conc.) was found to have the higher cohesive strength than SR-25 (high conc.) gel, which relates to the uniform strand length distribution ahead of the crack tip caused by “pulley effect” of the movable cross-links. The direct observation of the local stress/strain field of SR gels provides a direct evidence of“pulley effect” reducing the local stress intensification.