[Objective] There are many structural parameters of the opening spherical bulkhead, and it is time-consuming and laborious to directly use the finite element method to carry out parameter research.[Method] The geometric characteristic parameters of the opening spherical bulkhead were extracted and used as design variables to construct a surrogate model for the characteristic stresses of the spherical bulkhead with a single opening. After analyzing the correlation between the characteristic stresses and the structural parameters using the surrogate model, a combined surrogate model method with lower dimensions of design variables is proposed. The combined surrogate model consists of a surrogate model of characteristic stresses based on the cylindrical-toroidal-spherical shell parameters and a surrogate model of characteristic stress correction coefficients based on the opening fence parameters and the thickness of the spherical shell.[Results] The accuracy of the combined surrogate model was significantly improved due to the decrease in dimension of the design variables. Compared with the results of directly constructed surrogate model, the maximum error and the average error of the characteristic stress were reduced by 4.96%~22.95% and 0.59%~5.43% respectively. The single-opening combination surrogate model is used to predict the characteristic stresses of a typical spherical bulkhead with multiple openings, and the characteristic stress error is 0.12%~11.42%.[Conclusion] The proposed combined surrogate model for the strength of the spherical bulkhead with single opening can be used for rapid prediction of the characteristic stresses of spherical bulkheads with multiple openings.