The invention discloses a post-peak fractured rock triaxial slurry permeability test system and method. The system comprises a permeation system, an axial loading system, a circumferential loading system, a grouting pressure system and a data acquisition and analysis system. The method comprises the following steps: 1, debugging the test system and checking the running condition of the test system; 2, mounting a rock sample; 3, starting and setting the axial loading system; 4, starting and setting the circumferential loading system; 5, fracturing the rock sample to a post-peak fractured state;6, carrying out a grouting permeability test on the rock sample in the post-peak fractured state; 7, ending the test; 8, processing the test data. The permeability change characteristics of the slurry in the rock post-peak fracture process can be effectively determined; and the problems of unsmooth permeation of slurry in the fractured rock sample, easy blockage of the pipeline, non-uniform pressure action of the slurry, difficulty in confining pressure control, difficulty in sealing implementation and the like in triaxial slurry permeability test of different post-peak fractured state rockscan be greatly solved.