To study the stress condition at the junction of the spherical shell with opening nozzle, using the finite element analysis, a finite element model is built in view of the same spherical shell joining a flatting nozzle and inside-stretching nozzles with different inner lengths differently. The maximum stress and stress distribution are got. All kinds of stresses are obtained by the total stress which is carried on linear processing. The result shows the inside-stretching nozzle can reduce the maximum stress in comparison with the flatting nozzle, mainly reducing the local membrane stress, but not the peak stress. The maximum stress falls with increasing the inner length of the nozzle to some extent, and beyond the extent, the maximum stress tends to reach a stable value basically without changing the inner length. The stress variation can effectively provide a reference for improving the strength of the spherical shell.