Twenty　kinds　of　amino　acids　are　simplified　into　3　types:　hydrophobic　amino　acids　(H),　hydrophilic　amino　acids　(P)　and　neutral　amino　acids　(N).　Each　residue　is　reduced　to　a　bead　which　locates　in　the　position　of　the　C.　atom.　The　off-lattice　model　is　adopted　and　the　relative　entropy　is　used　as　a　minimization　function　to　predict　the　tertiary　structure　of　a　protein.　A　new　contact　intensity　function　is　given　to　consist　with　protein　design　research　based　on　the　relative　entropy.　Testing　on　several　real　proteins　from　Protein　Data　Bank　(PDB)　shows　the　good　results　obtained　with　the　model　and　method.　The　root　mean　square　deviations　(RMSD)　of　the　predicted　structures　relative　to　the　native　structures　range　from　0.30　to　0.70　nm.　A　foundation　for　studying　protein　design　using　the　HNP　model　and　the　relative　entropy　was　made.