A method for the determination of inorganic arsenic in water-soluble fertilizers was developed by using liquid chromatography-atomic fluorescence spectrometry(LC -AFS). The pretreatment conditions of samples were optimized.Under the optimal conditions，the linear correlationcoefficient( R)of As 3+ and As5+were 0.999 6 and 0.9998，and thedetection limit were 0.8 and 2.7 ng/mL respectively. The relative standarddeviation(RSD)of inorganic arsenic was in therange of 1.90%～3.66%，and the standard recovery was in the range of 91.9%～ 107.5%. This method has been applied to the determination of inorganic arsenic in several different types of water-soluble fertilizers with satisfactory results.