In order to solve the problem of difficult roadway support in deep crushed surrounding rock, the range of plastic zone is studied. Taking the roadway in the broken section of a mine as the engineering background, the current situation of roadway damage is investigated, and from the physical properties of the roadway surrounding rock itself, the elastic-plastic mechanics model applicable to this type of surrounding rock is established through theoretical analysis, the formula for calculating the radius of the plastic zone of the roadway is deduced, and the influence of cohesion and angle of internal friction on the plastic zone is analyzed in the condition of the coefficient of lateral pressure λ=1. Using Flac3D software, a numerical simulation model was established to verify the reasonableness of the theoretical calculation results. The investigation results show that: the reason for the damage of the roadway under the original support is the poor nature of the surrounding rock and the neglect of the plastic zone range by the support parameters; the numerical simulation shows that: the cohesion and the internal friction angle of the surrounding rock have a significant effect on the range of the plastic zone, and when the cohesion and the angle of the internal friction are large, the range of the plastic zone is small, and the enclosing rock of the roadway tends to be stabilized. Especially, when the internal friction angle is 35° and the cohesion is 3MPa, the change curve of the radius of the plastic zone turns, indicating that this combination of parameters is the key threshold of the bearing capacity of the surrounding rock. According to the theoretical analysis and numerical simulation results, the joint support scheme of “anchor (rod), net, spray + full-section anchor cable + base plate anchor cable” is proposed, and through the on-site displacement monitoring, the top and base plate displacement of 61mm and the displacement of two gangs of 40mm are successfully controlled, which effectively guarantees the stability of the tunnel surrounding rock. The results of the study provide theoretical basis and practical guidance for the tunnel support technology of deep broken surrounding rock.