In order to improve the fastening effect of the bolt flange of pressure vessel, the structure of the hydraulic wrench and the holding sleeve was improved, and the holding sleeve was optimized, and a new type of fixed wrench was designed. The paper introduced and compared the joint use of hydraulic wrench and holding sleeve in bolt flange fastening operation, improved the structure of the holding sleeve, and analyzed the static structure of the new type fixed wrench by ANSYS. The results show that the structure optimization can effectively improve the fastening effect of flange bolts of pressure vessel.