The relationship among plant functional traits is an ecological strategy that can enhance their own ability to use space resources, reflecting mechanisms of phenotypic plasticity that plants can adapt to the environment. By using the ArcGISestablished regional digital elevation model (DEM) and abstracting the slope aspect data of the study area, this paper studied the allometric relationship between height and crown width as well as height and diameter of Platycladus orientalis on different slope aspects of the northern mountains of Lanzhou with the method of standardized major axis estimation (SMA). The results showed that there were significant differences in diameters of P. orientalis on different slope aspects (P<0.05), and there were no significant differences in heights or crown widths on east and west slope aspects (P>0.05). There were slope aspect differences in the allometric relationship between crown width and height, which means the growth rate of crown width was greater than that of height on the south slope, but it is quite on the contrary on the north slope, in the meantime, the growth rates of height and width were similar on the west and east slopes. On all slope aspects, the growth rate of diameter was greater than that of height, and there was no obvious aspect difference in the allometric relationship between the diameter and height (P>0.05). The allometric relationships of height, crown width and diameter of P. orientalis were different on all slope aspects, which reflected the investment weighing mechanism on main components of P. orientalis in heterogeneous habitats.