NO₂^--N in secondary saline-alkali water in Northwest China has been at a relatively high concentration for a long time, which has seriously restricted the sustainable development of the saline-alkali aquaculture industry. Based on regular fixed-point monitoring of the Caowotan Fisheries and Agriculture Demonstration Area (104°7'40″E, 37°19'6″N) in Jingtai, Gansu, inorganic nitrogen conversion in different types of secondary saline-alkali water and its correlation with environmental factors were studied by paired sample t test, Duncan multiple comparison, and Pearson's correlation analysis. The results showed that:(1) inorganic tri-state nitrogen (NO₂^--N, NH₄⁺-N, NO₃^--N) and total nitrogen (TN) in the secondary saline-alkali water were at high concentrations and fluctuated seasonally[NO₂^--N (0.3±0.2) mg/L, NH₄⁺-N (1.93±1.25) mg/L, NO₃^--N (2.92±1.5) mg/L, TN (13.91±5.85) mg/L]. The proportion of inorganic nitrogen in TN was below 50%, indicating that the proportion of organic nitrogen in secondary saline-alkali water was higher; (2) pH was positively correlated with NO₂^--N, negatively correlated with NO₃^--N, and salinity was negatively correlated with NO₃^--N, pH and salinity aggravated the accumulation of NO₂-N; (3) aquaculture significantly reduced NO₃^--N and carbonate alkalinity in secondary saline-alkali water, showing ecological improvement of saline-alkali aquaculture to secondary saline-alkali water.