The paper studies the forming process of high inner-pressure hydroforming of T-branch tube by using DYNAFORM finite element simulation software based on its technology characteristics. First, the effects of different loading paths of key parameters(internal pressure, axial extrusion force, radial back force) on T-branch tube hydroforming process have been studied. The studies show that enough feed rate is essential to obtaining a certain branch height but excess feed rate can lead to the thickness seriously increased. The way of influence of internal pressure is contrary to radial back force, both excess internal pressure and slight radial back force can cause top branch thinned or fractured. If branch height is too low, radial back force will obstruct the extension of tube and productions cannot be compliance with design requirements. Second, the effects of coefficient of friction and radius of round angles on forming quality of T-branch tube have been discussed. The studies show that forming quality is better when the coefficient of friction is smaller or radius of round angles is larger.