Abstract: A simplified off-lattice model of protein is studied with a PSO algorithm.Interaction between atoms is represented by a physical-based potential.The protein's RMSD value between computed and experimental structures is 6.12Å in optimizing the potential in global space. The protein total energy and radius of gyration at PSO steps and the relation between minimum energy and corresponding RMSD value are investigated.It shows basic characteristics of protein folding.

Key words: off-lattice model, PSO algorithm, protein folding