The deformation and failure mechanisms of tunnels in jointed rock mass with variable orientation and overburden pressures were studied by physical modelling. The deformation and expansion characteristics and regularities of joints and its influence on the stability of tunnels were analyzed. The results shown that the effects of unloading and reactivation of joints, and subsequent shear slip and deformation induced by excavation cause the structural instability of tunnels. The deformation, failure, and instability of surrounding rocks are essentially the continued deformation and repeated failure of joints in varied stress field caused by excavation and overburden pressure. When the dip angle of the joint sets is 75°, the joints have extremely striking influence on the stability of tunnels. In addition, with the increasing of the overburden pressures, the deformation extent and failure rate are sped up prominently due to the rapid increasing of the shear stresses on joint planes.