Aimed at the large deformation of aircontrolled annular blowout preventer(BOP) rubber core in sealing process,and the difficulty in calculating the sealing pressure with the tubing,the physical model of the rubber core was set up.Combining the thickwalled cylinder theory with rubber constitutive equation,and by considering the material nonlinearity and geometric nonlinearity of the rubber core at the same time,the rubber core deformation and the contact pressure during the sealing process of the BOP were investigated.According to the different stress conditions during the nodeformation stage,free deformation stage and contact deformation stage of rubber core deformation process,the control pressure to each discrete micro segment was applied by using iterative methods,and the deformation and the contact pressure of the rubber core under different control pressures were obtained.The theoretical analysis results were compared with the simulation results.The results show that,in the stage of free deformation,with the increasing of control pressure,the deformation of the plastic core is gradually increased,and it is gradually decreased from the middle to both sides.In the stage of contact deformation stage,the inner diameter of the rubber core remains unchanged and the contact pressure between the rubber core and the tubing is increased continuously.The change rule of contact pressure calculated by the theory method of rubber core deformation is basically the same as simulation result,which verifies the correctness of the theoretical calculation method of rubber core deformation.