Taking the karst tunnel on a highway in Sichuan Province as the engineering target, an indoor scaled model is constructed by using similarity theory to study the effects of a rockfall action on tunnel arch protection and lining structures under different working conditions. The motion trajectory of a rockfall action is captured by a high-speed camera, with the strain response of the lining structure monitored by using strain gauges and a dynamic signal testing and analysis system, followed by a study on the acceleration response of the structure by using an accelerometer. Research has found that the rebound energy of a rockfall action gradually decreases, leading to a decrease in their rebound height; the acceleration and displacement response of the arch top position of the lining structure are significant, with the strain change of the lining structure increasing significantly with the increase of rockfall mass and height.