The invention relates to a surface-modified carbon molecular sieve, a chromatography filler composition, a chromatographic column used for dissolved gas analysis for transformer oil and a preparing method of the chromatographic column. The surface-modified carbon molecular sieve is prepared by a method including steps of dissolving picric acid into ethanol to prepare a coating and dipping solution, adding a carbon molecular sieve into the coating and dipping solution, and drying the mixture to fully volatilize the ethanol so as to obtain the surface-modified carbon molecular sieve, wherein the mass of the picric acid in the coating and dipping solution is 2-10% of the mass of the carbon molecular sieve. The surface-modified carbon molecular sieve is prepared by treating the carbon molecular sieve with the ethanol solution of the picric acid, and can be used for manufacturing the chromatographic column used for on-line dissolved gas analysis for transformer oil. Complete base line separation of seven dissolved gas components in the oil of large-scale transformers can be achieved at a constant temperature, and demands of on-line chromatographic detection can be met.