Terrestrial ecosystems generally contain various plant types (e.g. dicots, monocots, gymnosperms), and an evaluation of the dominant plant type in an ecosystem is the key to understanding geological records in paleoenvironmental research. In this study, we examined n-alkane chain length distributions in terrestrial higher plants in the central Chinese Loess Plateau, and found that average chain length (ACL) could be utilized as an indicator for differentiating gymnosperms from angiosperms. ACL21–33 was less than 27 for gymnosperms, but more than 27 for angiosperms. Moreover, a derived Pv index from a selected n-alkane ratio, (i.e. (C31 + C33)/RCn(n=27–33)), provided a relative criterion for distinguishing between dicots and monocots within the angiosperms. When Pv < 0.1, the ecosystem was predominated by dicots, but those with Pv > 0.1, were dominated by monocots. Discrimination of the dominant plant type in an ecosystem is important when leaf wax n-alkanes are used as a proxy for paleoenvironmental reconstructions.