This study introduced three presumed springs to imitate the three dimensional bolstering function of the bracket-tooth-periodontal tissue on the archwire with three dimensional finite element method (FEM), and, systematically analysed the force system produced by the "T" loop retraction archwire on the incisors. The following conclusions were drawn; (1) The activation of the "T" loop retraction archwire will produce extrusion and root lingual torque force as well as horizontal force on the incisors; (2) Adequate torqul on the incisor segment and gable bend mesial to the T-loop are necessary to control the position of the anterior teeth while they are being retracted; (3) retraction archwire should not be activated too much; (4) Lighter wire will produce milder and more durable forces.