Tests and analysis with the finite element method (FEM) have been used to study the behavior of Q460 welding neck flanges joints under axial compressive load. Flange modes of FP2121 and FP2727 were selected and the flange joints were subjected to axial compressive loads. The ultimate bearing capacity of the joints considering large elastoplastical deformation were analyzed by using the finite solid element. The result shows that the failure mode of the joints is the local buckling of the pipes, while the strength of the flanges is more than enough. The two circular fillet welds at neck and bottom have effects on the load transmission. The ratio of load transmission due to neck and bottom fillet weld is 3∶1, which is consistent to the testing results.