The invention discloses a method for estimating ultimate bearing capacity of a pressure-resistant spherical shell of a high-strength steel submersible. The method comprises the steps of 1: setting spherical shell related parameters including the mean diameter r of the spherical shell, different thickness values t and different yield strength sigma y; 2: researching the influence of the yield strength of a material on the bearing capacity of the spherical shell; defining the influence of the yield strength on the ultimate bearing capacity of the spherical shell as a plastic attenuation factor kp and performing solving; 3: obtaining a perfect nonlinear critical buckling load Pnon:pnon=kppm t of the spherical shell; 4: researching a law of influence of geometric initial defects on the buckling load of the spherical shell, and defining the influence of the geometric initial defects on the ultimate bearing capacity of the spherical shell as a geometric defect attenuation factor kimp and performing solving; 5: concluding an estimation formula for the ultimate bearing capacity Preal of the spherical shell: preal=kpkimppm t; and 6: according to related parameter values of an actual shell, searching for corresponding data, substituting the data into related formulae, and finally working out the required ultimate bearing capacity Preal of the spherical shell.