In order to clarify some basic rules between splitting extrusion deformation and splitting angle range of 45°120°, by taking the rectangular groove with 10 mm width and 10 mm height as the research object, the deformation process of splitting extrusion was studied by cusp splitting wedge with 30° splitting edge angle, using method of numerical simulation. The results show that as the splitting angle being increased, the sunk angle length decreases and the range of it decreased becomes flat gradually; the maximum grooveside swelling height gains and the range of it gained becomes flat gradually as well; the influence width being decreased, the volume of the waste increases in an almost linear relationship. As the splitting angle being increased, the peak forming force gradually increases and it gains faster in the initial stage, but it is late to enter the steadystate deformation stage and the stroke of steadystate deformation stage becomes shorter; unlike the initial stage, the slope of the forming force declines in the stage which the waste has been pushed out changes little as the splitting angle changes. As the splitting angle being increased, the inflection point of forming force downward appears earlier and shortens the force stroke, but does more work. Splitting angle should be small considered from the point of technology applications.