This study aimed to expound the effects of the changes in plant and soil environments on spatiotemporal distribution of nitrogen component accumulation under the arbuscular mycorrhizal fungi inoculation in rocky desertification areas. The Fraxinus malacophylla was selected as the host plant and it was inoculated with Funneliformis mosseae (FM), Claroideoglomus etunicatum (CE), and Rhizophagus intraradices (RI), using no fungal inoculation as the control treatment. The effects of changes in plant growth and soil physicochemical properties on the spatiotemporal variations in soil nitrogen components (i.e., total nitrogen, hydrolyzabl nitrogen, ammonium nitrogen, nitrate nitrogen) and their proportion (i.e., hydrolyzable nitrogen/total nitrogen, ammonium nitrogen/total nitrogen, nitrate nitrogen/total nitrogen) were identified under different AM inoculation. The results were as follows: 1) AM fungal inoculation significantly increased the values of soil nitrogen components and their proportion (P < 0.05). Compared with the control, the concentrations of the four nitrogen fractions increased from 12.09% to 156.88% in three fungal treatments, while the increasing rates of the proportion of hydrolyzabl nitrogen, ammonium nitrogen, and nitrate nitrogen in total nitrogen ranged from 13.25% to 60.07%. The increase in the vales of soil nitrogen components and their proportion ranked as FM > CE > RI. 2) The levels of soil nitrogen components and their proportion had spatiotemporal variations in the three fungal inoculation treatments. The maximum accumulation of the total nitrogen occurred in June, while that of the other nitrogen components occurred in September. They all decreased along the soil layer and the order of reduction magnitude for the four nitrogen components was FM > CE > RI. The maximum proportion rates of the hydrolyzable, ammonium, nitrate components were all in September. The proportion of the three nitrogen components decreased along the soil layer and was ranked as FM > CE > RI. 3) The AM fungal treatments significantly increased ground diameter, tree height, root biomass, soil carbon components (total organic carbon, readily oxidizable carbon, and microbial carbon), phosphorus components (total and available phosphorus), potassium components (total and available potassium), and water content compared with that of the control. In contrast, they significantly decreased soil pH and bulk density. The total organic carbon was at its maximum (72.25%) under FM treatment, while the available phosphorus was at its minimum (1.49%) under RI treatment. 4) Redundancy analysis showed that total organic carbon, readily oxidizable carbon, microbial carbon, and total phosphorus were the main driving factors affecting nitrogen component accumulation, while root biomass, readily oxidizable carbon, and microbial carbon were the main controlling factors of nitrogen component proportion. Therefore, AM fungal inoculation promoted nitrogen component accumulation and proportion through mediating the alterations in root biomass as well as soil carbon and phosphorus concentrations.