NH₄⁺ and NO₃^- are two main inorganic N sources available for plant growth. Rice is generally considered preferable to NH₄⁺ , but it also grows well under NO₃^- condition. In the past, most reports on NH₄⁺ and NO₃^- nutrition of rice were conducted under hydroponic conditions at about pH 6.0, but little research has been done on NH₄⁺ and NO₃^- nutrition of rice under acidic conditions. With the aggravation of soil acidification and the use of some marginal acidic soils for rice cultivation, it is of great significance to study NH₄⁺ and NO₃^- nutrition of rice under acidic conditions. In this paper, the effects of NH₄⁺ and NO₃^- on the growth, N efficiency and mineral nutrient contents (N, P, K, Ca, Mg, Fe, Zn, Cu, and Mn) in rice were studied under hydroponics at pH 5.0 with or without pH buffer MES. The results showed that, although there was no significant difference in above-ground growth (plant height, chlorophyll content, and dry weight) between NH₄⁺ and NO₃^- without adding MES, the above-ground growth of rice with NH₄⁺ was better than that with NO₃^- when MES was added. Root growth (root length, root surface area, and root weight) of NO₃^- treatment was superior to that of NH₄⁺ regardless of adding MES or not. There was no difference in N content and N use efficiency between NH₄⁺ and NO₃^-. However, N uptake efficiency of rice with NH₄⁺ was higher than that of NO₃^-. Compared with NO₃^-, NH₄⁺ increased the contents of P and Fe, decreased the contents of Ca, Mg, Zn, Cu and Mn, and had little effect on K content in rice shoots. These results indicated that NH₄⁺ facilitates shoot growth, N uptake efficiency and P and Fe contents in rice shoots, while NO₃^- is beneficial to improve rice root growth and Ca, Mg, Zn, Cu and Mn uptake by rice.