Nitrogen and phosphorus deficiencies and seasonal drought are major problems of plantations in coastal sandy land of Fujian. Nutrient resorption can reduce dependence of plants on soil nutrients supply, thereby enhancing their ability to adapt to adversity. Casuarina equisetifolia, Acacia cunninghamia and A.aulacocarpa artificial plantations in the coastal sandy land of Fuzhou city were taken as objects, and nitrogen and phosphorus concentrations and stable nitrogen isotope abundance values (δ¹⁵N) in leaves at different ages (mature leaves and senescent leaves) were determined. The nitrogen and phosphorus resorption efficiencies of leaves (NRE, PRE), resorption proficiency (NRP, PRP) and their relationship with biological nitrogen fixation rates were studied by statistical methods. The results showed that (1) the NRE of leaves of different nitrogen fixing tree species in the coastal sandy land was sequenced as A.aulacocarpa (52.80%) > A.cunninghamia (28.27%) > C.equisetifolia (24.63%). The leaf NRE of A.aulacocarpa was significantly higher than those of A.cunninghamia and C.equisetifolia, but there was no significant difference between the latter two species. The PRE of leaves followed the order of A.cunninghamia (74.08%) > A.aulacocarpa (63.99%) > C.equisetifolia (40.47%), and there was significant difference among them. (2) The biological nitrogen fixation rates of different nitrogen fixing trees in coastal sandy land listed in the order of A.cunninghamia (69.45%) > A.aulacocarpa (69.15%) > C.equisetifolia (34.59%). There was no significant difference in nitrogen fixation rate between the two Acacia species, however, the biological nitrogen fixation rate of the two Acacia species was significantly higher than that of C.equisetifolia by 99.88%~100.77%. (3) The biological nitrogen fixation rates of different nitrogen fixing trees was negatively correlated with NRE, PRE and NRP, and positively correlated with PRP. Therefore, there was a coupling relationship between nutrient resorption and biological nitrogen fixation (BNF) in different nitrogen fixing tree species in the coastal sandy land, and BNF significantly affected NRE, PRE, NRP and PRP. The results would provide a basis for revealing the adaptation mechanism of different nitrogen fixing tree species to barren soil and seasonal drought in coastal sandy land, and also provide a reference for forest management.