Unreinforced masonry structures usually suffer severe damage under strong earthquakes, and slip damage is one of the causes of structural failure. Slip will lead to insufficient wall damage and premature failure, affecting the overall seismic performance of the structure. Therefore, studying the slip failure behavior of unreinforced masonry walls will help mitigate the hazards of masonry structures. This study conducted a quasi-static test on two unreinforced masonry walls and established a finite element model based on the test results. Then, parameter analysis was conducted, and the influence of the axial compression ratio on the wall failure mode was studied. The research results show that a low axial compression ratio can easily lead to the slip of the wall, while an appropriate axial compression ratio can help increase the ultimate bearing capacity of the wall.