Abstract: In order to solve the dfficult support problem of Jurassic water bearing ultra soft rock in Shajhai Mining Area of Xinjiang, based on the detail engineerin g geological survey, theoretical analysis, numerical analysis, indoor test and site test and measurement, an nonlinear high deformation mechanics design method was a pplied to study the deformation failure mechanism and cause of the ultra large cross section junction.The results showed that the deformation mechanism at the junctio n was a complex deformation mechanism with stability lost in the middle rock pillar, molecule water sucking swelling mechanism, gravity mechanism, water role, engine ering deviatoric stress and other factors. With the lateral level restraint added on the bolt support, the stress status of the rock mass was improved, the bidirectional mut ual control of the bolt could be realized and the integrated strength of the stability of the middle rock pillar could be enhanced.The constant resistance and high deforma tion coupling support was applied to fully release the plastic performance of the surrounding rock.Meanwhile over large deformation could be restricted.The monitoring「 esults show that the maximun two sidewalls convergence was 53 mm and the maximum floor-to-roof convergence was 34 mm. Thus the coordinate deformation of the su rrounding rock-support could have a good coupling support status and could ensure the engineering stability.