Water and sediment condition changed greatly due to natural conditions and human activities, which brought sediment and exogenous substances input influenced on the vegetation growth and element absorption in the tidal flat wetland in the Yellow River delta. Orthogonal test with three factors and four levels were established, and we selected Suaeda salsa as study object to examine the ¹⁵N absorption characteristics for S. salsa and sediment under different water-sediment conditions and nitrogen input using ¹⁵N tracer technique. The results showed that the influence of water depth, sediment burial depth and nitrogen input on sediment total nitrogen content did not reach significant level, while nitrogen input had significant influence on sediment ¹⁵N derived from fertilizer (N_dff) and proportion (N_dff%), and the maximum values (10.44 mg/kg and 3.83%) were observed at W₄S₂N₃ (30 cm water depth+3 cm sediment burial+6 g/m² nitrogen input) treatment. Stem and leaf total nitrogen content, N_dff% and N_dff reached maximum value at higher water depth and sediment burial level, while root total nitrogen content, N_dff% and N_dff were higher at high nitrogen input level. The maximum values of root N_dff% (18.21%) and N_dff (1.10 mg/kg) were observed at W₁S₄N₄ (2 cm water depth+12 cm sediment burial +9 g/m² nitrogen input) treatment, and the growth of S. salsa was best at this treatment. So we concluded that proper control of water depth, sediment burial, and high nitrogen input (9 g/m²) was conducive to nitrogen absorption by roots, and then promoting the S.sasla growth. Consequently, the control of water depth, sediment burial and nitrogen input plays an important role in maintaining the health of tidal flat wetland under the background of large variation of water and sediment condition in the Yellow River delta.