Disclosed in the present invention is a method for detecting a
protein having changes in an energy state, and affinity of a ligand to a
protein. Specifically, after the energy state of a
protein changes, the tolerance to
enzyme cleavage destruction changes, the structure of the protein in a low-energy state is also destroyed under a non-denaturation condition by using a large amount of enzymes, and a
small peptide fragment which has a molecular weight of less than 5 KDa and can be directly used for bottom-top
mass spectrometry analysis is directly generated. The method has extremely high sensitivity, and
quantitative proteomics is used to find
enzyme cleavage differential
peptide fragments, and proteins to which the differential
peptide fragments belong and the positions in the proteins are analyzed, so that a protein having changes in an energy state, and a change region can be determined in the whole
proteome range. If the energy state of the protein changes due to addition of a ligand, the method can determine a
binding protein and a binding region of the ligand; and the output of a
quantitative result on the
peptide fragment level further enables the method to determine the local affinity of binding of the ligand to the protein.