Studying the effects of different nitrogen application amount on soil fertility before spring sowing could help determine the suitable nitrogen application amount in Hetao Irrigation Area. In this study, four nitrogen application levels (high-nitrogen N₃:325 kg/hm², medium-nitrogen N₂:225 kg/hm², low-nitrogen N₁:125 kg/hm², and no nitrogen application N₀) were set up in the field experiment. The spatial and temporal distribution of water and salt and the changes of total nitrogen, alkali-hydrolysis nitrogen and organic matter contents were studied during freezing-thawing period. Then the soil fertility was evaluated by principal component analysis. The results showed:Firstly, after autumn water application, soil moisture content was significantly higher than before. The surface soil moisture content increased. When it just began to freeze, soil water accumulated to surface layer, and then froze to the deeper layer as the temperature reduced. The irrigation rates were the same in different treatments. The impacts of different nitrogen treatments on the soil moisture content was not significant. The soil moisture could meet the crop water demand. The soil salinities increased with the increasing nitrogen application rates during the growth period. A large amount of salt was leaching when water was applied in autumn. Soil salt was subjected to the combined effects of infiltration and evaporation during the water thawing, resulting in that the surface soil salinities were N₀(0.14%) < N₁(0.17%) < N₂(0.19%) < N₃ (0.45%). Secondly, during freeze-thaw period, soil nutrients were mainly concentrated in the surface soil layer of 0-20 cm. During the freeze-thaw period, the contents of total nitrogen, alkali-hydrolysis and organic matter in the soil showed a change pattern of first increasing and then decreasing. The maximum value occurred in the maximum freeze-thaw period, indicating that freezing helped the accumulation of total nitrogen, alkali-hydrolysis and organic matter. The last, soil fertility was comprehensively evaluated before the next spring sowing. Organic matter, organic carbon and total phosphorus on PC1 and PC2 had higher factor loads, contributing to soil fertility. Considering from the composite scores (N₃ < N₀ < N₁ < N₂), high nitrogen treatment led to the low soil fertility, and the highest scores were given in the medium nitrogen treatment, resulting in the highest soil fertility. Therefore, it is, recommended that the nitrogen application rate should be around 225 kg/hm² for the maize growth, and 20% for the basal, 40% for the jointing stage and 40% for the tasseling stage respectively. This fertilization will be beneficial for the improvement of the soil fertility in the following spring sowing and also for the agricultural sustainable development.