Two unusual tricyclic terpanes (compounds X and Y) and four tetracyclic terpanes (compounds X1, Y1, Z, and Z1) have been detected in crude oils from the Pearl River Mouth, Beibuwan, and Liaohe basins in China. On the basis of their elution order, relative retention times in m/z 191 mass chromatograms, and their diagnostic ion fragments, we have identified two tricyclic terpanes (marked by peaks X and Y in previous literature) as C-21 and C-25 tricyclic terpanes and four tetracyclic terpanes (marked by peaks Xl, Yl, Z, and Z1) as C-24-des-A-lupane, C-24-des-A-oleanane, C-24-des-A-ursane, and C-27 tetracyclic terpane, respectively. These six compounds have similar characteristics to oleanane, ursane, and lupane in their chemical structure and are considered likely to originate from alcohols or ketone precursors present in higher plants. The high abundance of these tri- and tetracyclic terpanes is probably related to the distinctive contribution of higher plant material in the organic matter content of source rocks. In addition, the redox conditions and water depth in the depositional environment significantly impact the distribution patterns of the compounds, and it is possible that they are readily formed under oxidation conditions. Because of their unique biological origin and prominent geochemical significance, they may have potential application in oil-source correlation and the classification of crude oil families.