Abstract: To study the fractal characteristics of stylolite and its influence on the strength of limestone, the fractal dimension of horizontal stylolite and vertical stylolite was analyzed using the power spectral density method and the digital image box dimension method based on digital image processing technology. The influence of the stylolite on the limestone strength and the crack evolution process of the limestone were studied through experimental tests and numerical simulations. The results show that the fractal dimension of stylolite lies between 1 and 2, indicating that the stylolite is a self-affine fractal structure in nature, and the vertical stylolite has a large roughness. The stylolite weakens the strength of limestone by about 20% on average, the strength of limestone with different inclinations of stylolite shows less obvious anisotropy and stylolite has negligible effect on the elastic modulus of limestone. In the failure process of limestone, crack initiation and propagation in limestone is closely related to the stylolite, and the stylolite accelerates the damage and failure of the limestone. Numerical simulations show that the thickness, position, numbers, and fractal dimension of the stylolite have significant effect on the strength of the limestone.