Abstract Many numerical approaches have been proposed to simulate the folding process of origami pattern under external force or displacement. Based on the Finite Particle Method (FPM), this paper develops a method to simulate the unfolding process of the Origami Pattern named triangular Resch Pattern by the energy stored in the crease. The formulations of the FPM for particle-bar-hinge models are derived. A simple fold origami example is given to verify the proposed formulations. Finally, the unfolding process of the triangular Resch pattern is simulated, and the symmetry properties of the triangular Resch pattern are obtained. The symmetry properties of this pattern have potential use in the degree-of-freedom reduction and motion control.