Abstract: Incubation experiment was conducted to study the effects of different organic material additions on the inorganic nitrogen conversion in coastal saline-alkali soil, including seven treatments: CK(control), N (N fertilizer, ammonium sulfate), N+B (N fertilizer with biochar), N+M (N fertilizer with chicken manure), N+S (N fertilizer with straw), N+BM (N fertilizer with biochar, and chicken manure), N+SM (N fertilizer with straw, and chicken manure). The results show that, N fertilizer promoted the occurrence of nitrification and mineralization, increased soil ammonium throughout the incubation period. Compared with the N treatment, the N+B treatment held a certain amount of ammonium nitrogen, delayed the conversion of ammonium nitrogen to nitrate nitrogen, with its ammonium nitrogen content to be 1.85 times as that of N treatment, and inhibited soil nitrogen mineralization and nitrification, while decreased soil nitrate and mineral nitrogen by 24.77% and 55.86%, respectively. The N+M treatment promoted soil nitrification and mineralization, reduced soil ammonium by 29.79%, and finally increased soil nitrate and mineral nitrogen by 24.32% and 73.19%, respectively. The N+SM treatment had a similar effect as the N+M treatment, which increased soil nitrate and mineral nitrogen by10.33% and 35.01%, but having no significant influence on soil ammonium. The N+S and N+BM treatments had no significant effect on soil nitrification and mineralization. Therefore, for the comprehensive improvement and utilization of coastal saline-alkali soil, the addition of chicken manure can increase the content of mineral nitrogen and provide more nitrogen for plant growth, but it can promote soil nitrification and increase the content of nitrate nitrogen in the soil, bring about increased N₂O emissions and the risk of nitrate pollution of groundwater; while biochar has the effect of inhibiting soil nitrification and mineralization, it can hold more ammonium nitrogen and delay the nitrification of ammonium nitrogen, and reduce the loss of organic nitrogen. Biochar is an excellent organic material additive for saline soil reclamation.