The invention relates to the technical field of molecular dynamics simulation, in particular to a protein force field, and more particularly relates to a coupling dihedral angle parameter optimizationmethod based on a CMAP potential function. According to the optimization method, an existing protein force field is taken as a parent force field, local intrinsic conformation preference in a crimp library is taken as a fitting target, and dihedral angle parameters of amino acid residues in the parent force field are optimized, so that local conformation distribution obtained through molecular dynamics simulation and distribution in the crimp library reach preset similarity. The invention also relates to a protein force field obtained by the optimization method. According to the method, coupled dihedral angles in protein molecules can be simply and efficiently optimized at the same time, the dihedral angle parameter optimization process is simple, efficient and automatic, the residue specific force field RSFF2C with high compatibility is obtained, and the method can be widely applied to various kinds of MD software.