In response to the problem of leakage caused by the extrusion failure of the sealing ring when the pulley under pressure is subjected to ultra high pressure in the working environment,combining the sealing structure and sealing principle of the sealing pulley,the finite element analysis model of the sealing structure was established,and the cause of the sealing failure was analyzed.It is found that the main reason for the failure of the sealing ring is that the gap between the inner and outer shells is too large,because the outer shell and inner shell of the pulley under pressure are clearance fit due to considerations of machining accuracy and cost,the excessive clearance between the inner and outer shells is produced when subjected to medium pressure and cable weight under actual working conditions,and there is also a certain gap between the rectangular retaining ring set on the pressure bearing surface of the sealing ring groove and the inner wall of the shell for ease of assembly.The O-ring cannot compensate for the larger gap between the inner and outer shells,and it will be squeezed into the gap under the pressure of the medium,and a stress concentration is also produced.An optimization scheme was proposed to replace the rectangular retaining ring with a triangular retaining ring.Through finite element analysis,it is found that the triangular retaining ring can effectively compensate for the gap between the inner and outer shells,preventing the sealing ring from being squeezed out and damaged.