Existence of some holes at internal ribs enhances the function and value of the tubes. A new extrusion method is proposed here for the forming of this shape by extrusion with joining. The method involves the use of a unique mandrel that has a slit along its axis and two guides at the slit exit. A holed sheet is fed through the slit and joined with the inner surface of extrude tube. Effect of two parameters, that are tube-wall thickness and guide position h which is distance from guide top to die surface were clarified by FEA. Two kinds of three-dimensional analysis models were prepared. One of the analysis models treats the rib as rigid body to examine a gap between rib and tube. Another model treats the rib as the elasto-plasticity body as well as the billet to examine the effect of the guide position and the tube wall thickness on the rib deformation. The series of analyses was carried out with emphasis on the metal flow. The gap between tube and rib is able to be suppressed small and joining condition becomes satisfactory when guide position rose or tube wall was thin. When the guide position rose further, or the tube wall thickness was excessively thinner, the amount of the deformation of the rib increases, and it causes defects.