Estuarine marsh is one of the most sensitive ecosystems that respond to global change and human activities. The estuarine marsh generally acts as a sink of exogenous nitrogen (N), which might produce significantly influences on the processes of biogenic elements. In the background of enhanced exogenous N import in the Min River estuary, it is significance to explore the effects of N import on the distributions and key transformation processes of phosphorus (P) fractions in marsh soils. In this paper, the effects of exogenous N import levels (N_Nt, control treatment; N_Lt, low N treatment; N_Mt, medium N treatment; N_Ht, high N treatment) on P fractions in soils of Phragmites australis marsh in Shanyutan of the Min River estuary were investigated by in situ N enrichment experiment. Result showed that the exogenous N enrichment not only increased the total phosphorus (TP) contents in soils, but also altered its distributions in soil layers. The TP contents in soils of the N_Mt and N_Nt were approximated, but the values in soils of the N_Lt and N_Ht, compared with N_Nt, increased by 3.5% and 4.4%, respectively. The enrichment of N generally increased the contents of available and non-available P in soils, but reduced the values of moderately available P. Compared with N_Nt, the contents of available P in the N_Mt and N_Ht increased by 6.5% and 12.6%, while the values of non-available P in the N_Lt, N_Mt and N_Ht increased by 3.3%, 3.9% and 7.0%, respectively. It should be noting that the decline of moderately available P contents in the N_Mt was particularly evident and the deceasing amplitude reached 6.7%.The proportions of non-available P in TP in soils of different treatments were the highest (51.8%-54.1%), followed by moderately available P with 38.1%-41.2% and available P with 7.0%-7.9%. Moreover, the proportions of HCl-P_i, Residual-P, NaOH-P_o and NaOH-P_i in TP in soils of different enrichments were much higher, followed by Sonic-P_o and NaHCO₃-P_i, while those for NaHCO₃-P_o, Resin-P and Sonic-P_i were generally lower. This study found that the exogenous N enrichment altered the nutrient and acid-base conditions of soils greatly, which further influenced the distribution and availability of P fractions in soils. The increase of available P contents in the N_Mt and N_Ht, was mainly associated with Resin-P and NaHCO₃-P_o, while those of non-available P contents in the N_Lt, N_Mt and N_Ht was primarily related to Residual-P. By comparison, the significant increase of moderately available P contents in the N_Mt was mainly dependent on NaOH-P_i and Sonic-P_o.