Non-structural carbohydrates (NSC), nitrogen (N), and phosphorus (P) are important energy sources for plant growth, and their deficiencies affect plant growth factors. Magnolia sinensis is a rare and endangered species of wild plant in Sichuan province, and studies of its NSC, N, and P can reflect its nutritional supply level and adaptation strategies to the environment. The present study was conducted to evaluate M. sinensis at six altitudes (1840, 1960, 2070, 2170, 2270, 2390 m) in Lushan, and the NSC, N, and P content and their stoichiometry in the leaves at different altitudes were analyzed. The results showed that the soluble sugar content of M. sinensis in 2390 m leaves was significantly higher than that in 1840 m leaves. The NSC content at different altitudes was extremely significant, showing a unimodal change of "low-high-low" with increasing altitude. The NSC content of 2170 m leaves was the highest, and the carbohydrate supply was sufficient, ratio of soluble sugar/starch increased with altitude, N content and N/P ratio decreased with altitude, and N/P ratio was less than 14. The NSC/N ratio at 2390 m was significantly higher than that at 1840 m. The results showed that the soluble sugar and NSC content in the leaves of M. sinensis were not affected by the altitude, a higher soluble sugar content was beneficial for resisting the low-temperature environment, and growth was mainly limited by nitrogen but not by carbon. The protective strategies of NSC, N, and P in the limited distribution range of the endangered plant M. sinensis were determined, providing information on carbon metabolism and adaptation strategies used by this plant.