[Objectives] Food serves as the energy foundation for the survival and reproduction of animals, and its nutritional quality is of utmost significance for the development of animal individuals and populations. This study aims to evaluate the quality of bamboo, the staple food of Giant Pandas, in the Liziping National Nature Reserve, Sichuan Province. [Methods] The Liziping National Nature Reserve serves as both the distribution area and the release site for the small population of Giant Pandas Ailuropoda melanoleuca. The nutrient-to-energy ratios of protein, carbohydrate, and fat in the stems, leaves, and shoots of two bamboo species (Arundinaria spanostachya and Yushania lineolata) in this area were compared using the nutritional geometric model. [Results] There was no significant difference in the nutrient-to-energy ratio of nutrient provided by each vegetative organ between the two bamboo species. The bamboo shoots and leaves had significantly higher protein-to-energy ratios than stems, supplying more than half of the energy for Giant Pandas (Fig. 3, Table 1). Bamboo stems, especially those of multiple years, had a higher carbohydrate-to-energy ratio and could be used as an important energy source for Giant Pandas in winter and spring. The age of bamboo had no significant impact on the nutrient-to-energy ratio in leaves (Figs. 4, 5). The nutrient-to-energy ratios provided by the two bamboo species for Giant Pandas in the study area were similar to those in other distribution areas and could meet the energy demands of both wild and released Giant Panda individuals. [Conclusion] This study evaluates the quality of bamboo in the Liziping National Nature Reserve from the perspective of energy balance. It provides crucial basic information for the protection, restoration, and management of the Giant Panda habitat, particularly the bamboo forest, in this region.