Abstract: As a kind of magmatic rock, basalt widely exists in the engineering geological environment of human activities. To study the mechanical characteristics of arched basalt, this experiment used water-jet cutting technology to prepare the arched basalt samples with different height-span ratios. And then using the rigid servo machine, the arched basalt specimens were subjected to the axial and lateral confining loads, the failure process, the failure mode, the crack type, the local strain and the effect of height-span ratio on the crack propagation were analyzed. The results show that with the height-span ratio increasing, the peak strengths of the arched basalt samples show a downward trend. Owing to the presence of lateral restraint, the overall decrease of the peak strengths is relatively small. When the height of the arch exceeds 1/2 of the height of the rock sample, the peak strength decreases the most. The height-span ratio of the arch affects the crack propagation direction. With the increase in the arch height-span ratio, the failure cracks on both sides of the arch gradually move towards the middle, forming a shape similar to an inverted funnel. On the basis of the local strain analysis, it is found the middle part deformation gradually changes from micro-tensile deformation to micro-pressure deformation. Finally, the failure process of all samples always starts from the arch feet on both sides, and then the phenomenon of rock fragmentation and crack generation gradually appear. As the loading continues, the micro-cracks at the arch feet gradually develop to the top and run through the sample, resulting in the complete destruction.