<p>To study the crack penetration mechanism and failure characteristics of complex fissures rock mass under different filling materials, the spatial printing of complex fissures and the preparation of complex fissured rock-like specimens were realized based on 3D printing(3DP) technology. In this study, digital image correlation (DIC) was used to monitor the strain contour changes in the damage process of complex fissures rock-like specimens and to statistically analyze the propagation of fissures and the damage pattern of the specimens during the damage process. The results showed that the increase in peak strength of the specimens under HIPS, and low-strength gypsum filling was 56.34% and 29.11%, and the increase in modulus of elasticity of the specimens was 119.59% and 25.77%. The stress-strain curves of the complex fissures rock-like specimens showed the phenomenon of stress decreasing and then increasing several times. The cracks near the fissures on the outside of the specimen will be the first to propagate to form penetration cracks, and the propagation direction of the main penetration cracks is parallel to the stress loading direction. With the increase of filling materials strength, the main penetration cracks region gradually moves from the middle to both sides, and the main failure mode of the specimen changes from tensile-shear mixed damage to tensile damage. The lengths and angles of the pre-existing fissures in the main penetration region of the three types of specimens fall in the same interval.</p>