Instability of the equipment hatch's hoisting structure carrier occurs under the combined action of permanent and variable loads,and the accuracy of the ultimate load calculation results has an important influence on the design performance of equipment hatch.In engineering calculations,the traditional algorithm of directly solving eigenvalues without distinguishing load types resulted in overly conservative results.In this paper,on the basis of the original algorithm using ANSYS for buckling analysis,the loads that should not be amplified by the eigenvalues are distinguished.The eigenvalues are taken as the objective function,the reasonable ultimate loads are obtained through optimization iteration,and the correction coefficient is introduced in the iterative process to speed up the convergence.The accuracy of the improved engineering calculation method was verified through nonlinear analysis,and a suitable ultimate load algorithm for equipment hatch's hoisting structure carrier was found for engineering calculations.