In order to explore the mesoscopic mechanism of rock damage and the characteristics of precursor to destruction, the shear failure acoustic emission test was carried out on carbonaceous shale, the phase-space reconstruction and correlation dimension calculation of the three acoustic emission parameters were carried out by Grassberger-Procaccia (G-P) algorithm, and the evolution law of correlation dimension in the whole process of carbonaceous shale destruction was analyzed by using fractal theory. The results show that the acoustic emission activity is active in different stages of rock deformation, and there is a calm period. The acoustic emission ringing count, energy, and amplitude sequences all have fractal characteristics, and the correlation dimensions of the three show the change law of "ascending dimension-dynamic fluctuation-dimensionality reduction" in the whole process of destruction. The dimensionality reduction phenomenon occurs before the destruction of the rock and ends after the destruction of the rock sample, so it can be used as the precursor information of the rock instability failure as the calm period, and the dimensionality reduction phenomenon of the associated dimension of the ringing count and energy is more significant and lasts longer, which is more suitable as the precursor information of the rock instability failure than the amplitude.