In order to disclose the improvement effects of fulvic acid on soil with saline-alkaline disturbance and fertilizer effects under different nitrogenous fertilizer levels, a field experiment was conducted with the newly- reclaimed soil in the coastal tidal flat under rice-wheat cropping rotation. The effects of fulvic acid and different nitrogen levels on soil salinity control and soil fertility improvement were studied by measuring soil electric conductivity, pH value, organic carbon and the content and stability of soil aggregates. The results showed that fulvic acid could effectively reduce salt content in topsoil. When the nitrogen level was 300 kg/hm², the effect of fulvic acid were best on decreasing soil electric conductivity and pH value of topsoil (0–20 cm). Fulvic acid could effectively improve soil structure, compared with the nofertilizer control, water-stable macro-aggregates (>2mm) under the nitrogen level of 300 kg/hm² increased by 18.6% in wheat season and 13.8% in rice season, and the mean weight diameter of aggregates increased by 38% compared with the conventional fertilization treatment. In the initial stage of reclamation, the nitrogen level had a greater impact on organic carbon content of topsoil than fulvic acid. Compared with low nitrogen (225 kg/hm²) and high nitrogen (325 kg/hm²), the moderate nitrogen (300 kg/hm² ) increased total organic carbon accumulation in two seasons increased by 31.0% and 120.0% respectively. By comprehensively considering the effects of soil improvement, decrease of soil salinity, increase of water-stable macro-aggregates content, its stability and organic carbon content, fulvic acid combined with the appropriate amount of nitrogen is recommended as the optimal fertilization for the slight and moderate saline-alkali soil.