Hat-stiffened structures are widely used in aircraft. In order to ensure the safety of aircraft structures, stability analysis of such structures must be carried out. Taking the titanium alloy double skin hat-stiffened structure as the research object, the ultimate load of stiffened plate is calculated and analyzed by using the engineering estimation methods ' plate element method ' and ' cutting method ', and the ultimate bearing capacity and failure mode under axial compression load are studied. The calculation results are compared and analyzed by experiments. The results show that the error of the cutting method is 13.4 %. In contrast, the calculation results of the plate element method and the finite element simulation are very close to the real test values, and the errors are 4.5 % and 3.2 % respectively. For this type of structure, prediction by plate element method has certain engineering application value.