Abstract: In order to meet the needs of rapid construction of multi-angle drillings of tunnel core drill, and further improve the automation level of the angle adjusting mechanism to eliminate the hidden danger of the artificial auxiliary angle adjustment, a two-stage angle control mechanism is designed for the tunnel core drill to analyze the force of two sets of hydraulic oil cylinder in the angle adjustment device of drill rig and establish the mathematical model of force analysis. And by using the mathematical software MATLAB, the cylinder force was simulated with the actual engineering parameters of the drilling rig. The variation law in all adjustable range and limit value of the force for the two sets of angle regulating cylinders were obtained. According to the analysis results, the design of the angle adjusting cylinder was carried out.