In this study, whole-oil gas chromatographic fingerprint analyses were performed on oils from the Es33 reservoir in the Liubei area of the Nanpu Sag. The gas chromatographic peaks of cyclic and branched alkanes with relatively high resolution from nC10 to nC25 were selected to establish a database of whole-oil gas chromatographic peak height ratio fingerprints. Reservoir fluid connectivity was identified by using clustering analysis. This method can reflect the gas chromatography fingerprint information accurately and entirely, and avoid the one-sidedness of the star diagram method which only selects several fixed gas chromatographic peaks.