Arbuscular mycorrhizal (AM) fungi can form symbiosis with most terrestrial plants and provide important ecological services. Under the intensified nitrogen (N) deposition, more and more soil ecologists pay attention to the impacts of N deposition on AM fungal community. However, most relevant studies were carried out in grassland ecosystems, while studies on forest ecosystem were very limited. Moreover, most simulation studies in forest ecosystems applied N to the forest floor, ignoring the canopy processes, may not accurately reflect the natural situations. We conducted a field experiment on the influence of N addition mode (understory vs canopy) and rate on AM fungi in a mixed deciduous forest of China. The experiment had a fully randomized block design with four blocks (replicates) and each block included five plots. Within each block, each plot was randomly assigned with one of the five treatments:ambient (CK), canopy addition of N at 25 (CN25) or 50 kg hm^-2 a^-1 (CN50), understory addition of N at 25 (UN25) or 50 kg hm^-2 a^-1 (UN50). AM fungal alpha diversity indices and community composition were determined by high-throughput sequencing. The results showed that under the experimental conditions, AM fungal richness and Shannon diversity indices were not significantly altered by N addition mode, rate or their interactions. However, after one year of experimental treatment, N application mode showed a marginal effect on AM fungal community composition, while N application rate showed an extremely significant effect, and the treatment interaction was also significant. At N addition rate of 25 kg hm^-2 a^-1, the difference between canopy N addition and control was not significant, while the AM fungal community composition was significantly changed by understory N addition. At N application rate of 50 kg hm^-2.a^-1, canopy addition of N slightly altered AM fungal community composition, but understory of N application did not change AM fungal community composition. In the next three years, N addition mode, rate or their interactions all showed no significant effects on AM fungal community composition. Overall, the results indicated that understory application of N may overestimate the effect of N deposition on the AM fungal community under natural conditions at certain N application rate and time scale. AM fungal communities under different treatments tend to converge over time, suggesting that AM fungal community may have adapted to N deposition over time. This study evaluated the effects of different N application modes on AM fungal community in forest ecosystem. We could have a more comprehensive understanding of the ecological impacts of N deposition by considering broader N gradients and longer observation period in future research.