Abstract: Based on the engineering research background of Minxian tunnel in Dingxi section of national G75 Weiwu expressway, the surrounding rock type belongs to jointed-high stress-expansive ( JHS ) composite soft rock. In the process of tunnel construction, the original support design scheme has serious soft rock large deformation disaster. After analyzing its deformation mechanism, the mechanical transformation countermeasures for different mechanical mechanisms are proposed. The high pre-tightening force constant resistance large deformation anchor cable widely used in rock fields such as mines and edge breaking is introduced, and a new high pre-stress active and passive combined support technology of ' advance support + NPR anchor cable support technology + permanent lining ' is proposed. The numerical simulation method is used to simulate and compare the control effects of different support technologies. The results show that different support technologies all control the surrounding rock. By monitoring the deformation of surrounding rock and the stress of constant resistance large deformation anchor cable in the field test section, the control effect of large deformation support is remarkable. The maximum deformation of surrounding rock is only 73 mm, and the preload of constant resistance large deformation anchor cable is in the range of 280 ~ 300 kN, which effectively plays the role of constant resistance yield support.