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It is significant to develop a green ammonia preparation method for decreasing carbon emission. This work demonstrates a zero-carbon method for preparing ammonia feedstock consisting of a ratio of H 2 :N 2 ≥ 3:1 by direct electrolysis of air and steam as fuel gas through solid oxide electrolysis cell (SOEC). Through adjusting the working current and proportion of air/steam, the ratio of H 2 and N 2 can be achieved to more than 4:1, and the fuel is pure enough to be used for synthesizing ammonia. The production rate of ammonia feedstock reaches 1.79 × 10−6 mol/ (cm2·s), and the energy conversion efficiency (ECE) reaches 69.30 %. A stable 100 h electrolysis operation is carried out to generate H 2 /N 2 required for ammonia production. This work provides a new efficient method for the synthesis of green ammonia. • One-step method to produce feedstock for green ammonia is developed. • H 2 :N 2 ≥ 3:1 is achieved by direct electrolysis of air/steam through solid oxide cells. • The ammonia production rate reached to 1.79 × 10−6 mol/ (cm2·s). • A stable operation is observed for 100 h as required for ammonia production. • Partial Ni oxidation near the fuel inlet is the main cause of cell degradation. [ABSTRACT FROM AUTHOR]