Abstract: Based on the determination method of Sb(Ⅲ) and Sb(Ⅴ) in soil, a method for the determination of water soluble As(Ⅲ) and total arsenic in soil has been established by using Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS) in the media of 0.3 mol/L NaH₂PO₄-Na₂HPO₄. An amount of As(Ⅴ) was obtained by subtracting As(Ⅲ) from total arsenic. The hydrogen was provided from a hydrogen generator instead of chemical reaction to ignite a H₂-Ar flame. Therefore, arsenic in any media was measurable since the arsenic was reduced into AsH₃. Effects on the determination of As(Ⅲ) and As(Ⅴ) were investigated for concentrations of NaH₂PO₄-Na₂HPO₄ from 0.02 mol/L to 0.4 mol/L. The results show As(Ⅴ) can be screened by 0.3 mol/L NaH₂PO₄-Na₂HPO₄. The detection limits were 2.92 ng/g for As(Ⅲ) and 2.35 ng/g for total As. The recoveries of As(Ⅲ) and As(Ⅴ) are 96%-104% and 101%-103%, respectively. The method was simple and highly accurate, meeting the requirements for multiple sample analysis.