Atmospheric nitrogen (N) deposition is a process during which reactive N (including NH₄⁺ and NO₃^-) is deposited by the atmosphere into the soil and oceans. Over the last several decades, anthropogenic activities such as intensive agriculture and industry have caused a great increase in atmospheric N deposition. For example, the average N deposition rate in China has increased from 13.2 kg/hm² in the 1980s to 21.1 kg/hm² in the 2000s, and is projected to increase further in coming decades. Elevated N deposition will have many effects on forest ecosystems. Previous studies have shown that long-term N deposition will reduce plant diversity, inhibit the litter decomposition rate, change the soil microbial community structure, accelerate forest nitrogen saturation, cause soil acidification, and even alter the nutrient cycle. In recent years, the effects of atmospheric N deposition on the soil Phosphorus (P) cycle in forest ecosystems have received much attention, because P is one of the macronutrients essential to living organisms and is also the main limiting factor in most ecosystems. Although a series of studies were conducted that investigated the effect of N deposition on the soil P cycle in forest ecosystems, a general knowledge base has not yet been established. To rectify this, we used data from existing studies to summarize how N deposition affects the soil P cycle in forest ecosystems. The following aspects were described: 1) the concept of the soil P cycle in the context of forest ecosystems and 2) common methods used to study the effects of atmospheric N deposition on the forest soil P cycle, including long-term simulated N deposition, gradiated natural N deposition, and isotope tracing. In addition, 3) the results of previous studies on the effect of atmospheric N deposition on the forest soil P cycle were summarized. In general, atmospheric N deposition has a negative effect on the soil P cycle in forest ecosystems, in that it accelerates it. Three conclusions can be drawn about the effects of N deposition on three major soil P processes. Ⅰ) Concerning the effect of N deposition on the P input in soil: litter production and the return of P from litter to soil generally depends on the initial soil N status. In "N-rich" soil, extra N input decreases litter production and inhibits the decomposition process, thus decreasing the rate of P return, whereas in "N-limited" soil, N input promotes these processes. Ⅱ) Concerning the effect of N deposition on the internal transformation of soil P: long-term N deposition tends to weaken the mobility of P and decrease labile phosphate content. Microbial biomass phosphorus (MBP), an important source of labile soil phosphate in forests, also decreases under N deposition. Ⅲ) Concerning the effect of N deposition on P output in the soil: when plant growth is limited by N, N deposition will stimulate plant uptake of P, and therefore increase the leaf P concentration while decreasing the leaf N/P ratio; however, when plant growth is not limited by N, N deposition will decrease plant uptake of P and thus the leaf P concentration, increase the leaf N/P ratio. Thus, we identified the major mechanisms driving changes in soil P cycling induced by N deposition. First, N deposition will directly alter the quality of the soil organic matter, such as the C:N:P ratio. High C/P and N/P ratios inhibit the decomposition process and the return of P to the soil. Second, N deposition alters microbial communities. Fungi, especially mycorrhizal fungi, are more sensitive to N deposition than bacteria. Third, N deposition alters soil P cycling by increasing the concentrations of base cations such as Fe³⁺, Al³⁺, and Mn²⁺, which bond with HPO₄^2- and H₂PO₄^-. Finally, enzymes are also affected by N deposition. In N-saturated and P-limited soil, microbes and plant fine roots release phosphatase in order to accelerate the mineralization of organic phosphorus, which alleviate the soil P limitation. However, this increased phosphatase activity cannot not alter the low concentration of available P in the soil, because the mineralized available P will be taken up instantly by soil microbes and plant fine roots. Finally, we point out the limitations and problems with current studies, and suggest potential future avenues of research on the effects of N deposition on the forest soil P cycle.