<p>Grouting reinforcement technology is a method to reinforce fractured rock mass in rock engineering. Fillers will change the stress of the fracture, thus affecting the mechanical behavior and cracking behavior of the fractured rock mass. In this paper, uniaxial compression tests were conducted on red sandstone samples containing varying numbers of fractures, and the impact of fillers on the strength characteristics and damage progression in fractured red sandstone was investigated. A numerical simulation of the uniaxial loading process was conducted, examining the influence of fracture and filler presence on mesofailure mechanisms, focusing on mechanical properties, particle displacement and failure modes. The findings indicate that the filled specimens exhibit higher uniaxial compressive strength and elastic modulus compared to the unfilled ones. During the loading process, a phenomenon of stress concentration arises at the interfaces and tips of fractures, which subsequently triggers the formation of numerous microcracks. The emergence of fractures within the specimen leads to a substantial decrease in its crack initiation coefficient. When fractures are filled, the crack initiation coefficient significantly improves, requiring higher stress for failure. The damage evolution can be categorized into four stages: undamaged, initial damage, damage progression and ultimate failure.</p>