In engineering design, special area of pressure vessels always needs opening nozzles in order to satisfy complexity of technologies. Only considering the single load condition of the pressure vessels, the calculation of opening⁃nozzles in GB 150—2011 does not involve additional external load on opening⁃nozzles in practical projects. The SolidWorks software was used to locally model the tangentially opened pressure vessel of the cylinder, and the finite element analysis method was used to apply two internal conditions of the internal pressure and the external load of the internal pressure to the three⁃dimensional solid model to obtain the structural stress. Distribution and strength evaluation were carried out, and the influence of the additional external load on the structure of the pressure vessel was studied.The results show that the stress value in nozzle⁃vessel junction area increases sharply and it changes symmetrical distribution of stress in the connection between the nozzle and the vessel because of the external load of the nozzles. The analyzing results can provide some reference in stress analysis of the opening⁃nozzles with the united static load.