Many studies have observed that leaf wax delta Dn-alkanes values differed significantly between woods and grasses in modern plants, with grasses D-depleted by 40 parts per thousand-70 parts per thousand. The reasons for the differences in leaf wax delta D (n-alkane) values between woods and grasses, however, remain unclear. In this study, we measured the delta D values of soil water (delta D-sw), leaf water (delta D-lw), and leaf wax n-alkane (delta Dn-alkane) for woods and grasses. We found no significant differences in the delta D values of soil water (P = 0.82) and leaf water (P = 0.74) between the two life forms of plants. Therefore, the differences in leaf wax delta D (n-alkane) values between woods and grasses may correlate with inherent properties of different plant life forms, such as leaf structures, biosynthetic processes, and leaf morphologies. Moreover, it is also possible that soil water with different delta D-sw at different depths utilized by woods and grasses may be responsible for some of the differences in leaf wax delta Dn-alkane values between the two life forms of plants, if woods mainly use soil water from the > 100 cm depth, whereas grasses mainly use soil water from the < 100 cm depth. The results of this work allow us to better understand the leaf wax delta Dn-alkane values of different plant life forms in a region.