Abstract: The invention relates to a method for simulating an orthognathic operation, wherein, to simulate the displacement of the upper dental arch 105 of the patient caused by the surgical intervention to be applied to the maxilla 106 during said orthognathic surgery, the angular and translational position of an upper mounting plate 526 of a 3-D orthognathic surgery simulator 510 carrying a model 317 of said upper dental arch 105 is readjusted by rotating said upper mounting plate 526 around at least two, preferably three of three orthogonal axes X1Y and Z with respect to a rotation point 522 fixed to an arm 521 of said 3-D orthognathic surgery simulator 510, and translating said arm 521 substantially parallel to at least one of the same three orthogonal axes X, Y, Z.