It is generally believed that the binding energy value is less than 29.3 kJ mol-1, which indicates that receptor and ligand have a good affinity, and ESR1 and FOS have good binding free energy and docking fraction (docking fraction of FOS is −14.200, and binding free energy is −27.893 kcal/mol); ESR1 has a docking score of −15.833 and binding free energy of −30.001 kcal/mol, which may be a key drug target for treating gastric cancer. The gene discussed is FOS; the disease is gastric cancer.