Abstract: We explored the adaptation of Setaria viridis (L.) Beauv. to harsh sandy coastal environments in the core area of the Yantai Coastal Shelter Forest Nature Reserve by measuring the carbon (C), nitrogen (N), phosphorus (P), and potassium (K) content in mature and senescent leaves, analyzing their ecological stoichiometric characteristics and nutrient resorption efficiencies, and studying the coupling relationship between the two. Results showed that leaf N∶P was greater than 16 and the growth and development of S. viridis was more restricted by P. Leaf nitrogen resorption efficiency (NRE), phosphorus resorption efficiency (PRE), and potassium resorption efficiency (KRE) were (58.038 ± 2.973)%, (62.167 ± 5.301)%, and (86.557 ± 0.950)%, respectively. NRE and PRE were higher than the average plant leaf resorption efficiency in China and KRE was higher than the global average plant resorption efficiency. The leaf stoichiometric characteristics were strongly correlated with PRE, but slightly less correlated with NRE and KRE. Nutrient resorption efficiency of the leaves was mainly affected by the stoichiometric ratio of the senescent leaves. The nutrient resorption efficiency of S. viridis was high in the study area, with a certain correlation between the stoichiometric ratio and nutrient resorption. These results indicate that S. viridis exhibits strong adaptability to the barren environment, which is of great significance to the conservation of coastal protection forests.