Abstract: Nutrient limit at high altitude is one of the main formation mechanisms of global timberline. In order to explore the factors limiting the forest distribution at high altitudes in Changbai Mountains of Northeast China, this paper determined the total carbon (TC), total nitrogen (TN), and total phosphorous (P) contents in the leaves and one-year old branches of the tree species Betula ermanii and its associated bush species Rhododendron aureum in the Mountains, and analyzed the relationships of these nutrients contents with soil nutrients and altitudinal gradient. At altitude 1850-2050 m (timberline), the TC, TN, and TP contents in the two species leaves and one-year old branches had the same variation trend along the altitudinal gradient, and the N/P in all the organs was far less than 14, indicating that the growth of the two species was suffered from N limitation. In the meantime, as compared with that at low altitudes (below 1950 m), the TP content in all the organs of the two species at high altitudes was lower, suggesting that the two species on timberline were suffered from P limitation. The TN and TP contents of the two species had no obvious decreasing trend along the altitudinal gradient, suggesting that below the timberline (2050 m), the N and P limitations had no relationship with low temperature, while the patchy distribution of the two species above the timberline could be related to the soil nutrient supply.